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77-608: Domnitor , in full Principe Domnitor (Romanian pl. Principi Domnitori ) was the official title of the ruler of Romania between 1862 and 1881. It was usually translated as " prince regnant " in English and most other languages, and less often as " grand duke ". "Domnitor" is an adjective derived from the Romanian word " domn " ( lord or ruler ) and, in turn, from the Latin " Dominus ". The title Domn had been in use since

154-455: A fovea area which gives acute vision. In the acute zone, the eyes are flattened and the facets larger. The flattening allows more ommatidia to receive light from a spot and therefore higher resolution. The black spot that can be seen on the compound eyes of such insects, which always seems to look directly at the observer, is called a pseudopupil . This occurs because the ommatidia which one observes "head-on" (along their optical axes ) absorb

231-743: A massive plural and a numerative plural , the first implying a large mass and the second implying division. For example, "the waters of the Atlantic Ocean" versus, "the waters of [each of] the Great Lakes". Ghil'ad Zuckermann uses the term superplural to refer to massive plural. He argues that the Australian Aboriginal Barngarla language has four grammatical numbers: singular, dual, plural and superplural . For example: A given language may make plural forms of nouns by various types of inflection , including

308-460: A central point. The nature of these eyes means that if one were to peer into the pupil of an eye, one would see the same image that the organism would see, reflected back out. Many small organisms such as rotifers , copepods and flatworms use such organs, but these are too small to produce usable images. Some larger organisms, such as scallops , also use reflector eyes. The scallop Pecten has up to 100 millimetre-scale reflector eyes fringing

385-428: A cluster of numerous ommatidia on each side of the head, organised in a way that resembles a true compound eye. The body of Ophiocoma wendtii , a type of brittle star , is covered with ommatidia, turning its whole skin into a compound eye. The same is true of many chitons . The tube feet of sea urchins contain photoreceptor proteins, which together act as a compound eye; they lack screening pigments, but can detect

462-427: A factor of 1,000 or more. Ocelli , some of the simplest eyes, are found in animals such as some of the snails . They have photosensitive cells but no lens or other means of projecting an image onto those cells. They can distinguish between light and dark but no more, enabling them to avoid direct sunlight . In organisms dwelling near deep-sea vents , compound eyes are adapted to see the infra-red light produced by

539-641: A few facets, each with a retina capable of creating an image. With each eye producing a different image, a fused, high-resolution image is produced in the brain. The mantis shrimp has the world's most complex colour vision system. It has detailed hyperspectral colour vision. Trilobites , now extinct, had unique compound eyes. Clear calcite crystals formed the lenses of their eyes. They differ in this from most other arthropods, which have soft eyes. The number of lenses in such an eye varied widely; some trilobites had only one while others had thousands of lenses per eye. In contrast to compound eyes, simple eyes have

616-407: A focusing lens , and often an iris . Muscles around the iris change the size of the pupil , regulating the amount of light that enters the eye and reducing aberrations when there is enough light. The eyes of most cephalopods , fish , amphibians and snakes have fixed lens shapes, and focusing is achieved by telescoping the lens in a similar manner to that of a camera . The compound eyes of

693-612: A high refractive index, decreasing to the edges; this decreases the focal length and thus allows a sharp image to form on the retina. This also allows a larger aperture for a given sharpness of image, allowing more light to enter the lens; and a flatter lens, reducing spherical aberration . Such a non-homogeneous lens is necessary for the focal length to drop from about 4 times the lens radius, to 2.5 radii. So-called under-focused lens eyes, found in gastropods and polychaete worms, have eyes that are intermediate between lens-less cup eyes and real camera eyes. Also box jellyfish have eyes with

770-403: A lens focusing light from one direction on the rhabdom, while light from other directions is absorbed by the dark wall of the ommatidium . The second type is named the superposition eye. The superposition eye is divided into three types: The refracting superposition eye has a gap between the lens and the rhabdom, and no side wall. Each lens takes light at an angle to its axis and reflects it to

847-415: A lesser extent) dual are extremely rare. Languages with numerical classifiers such as Chinese and Japanese lack any significant grammatical number at all, though they are likely to have plural personal pronouns . Some languages (like Mele-Fila ) distinguish between a plural and a greater plural. A greater plural refers to an abnormally large number for the object of discussion. The distinction between

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924-447: A limit on the possible resolution that can be obtained (assuming that they do not function as phased arrays ). This can only be countered by increasing lens size and number. To see with a resolution comparable to our simple eyes, humans would require very large compound eyes, around 11 metres (36 ft) in radius. Compound eyes fall into two groups: apposition eyes, which form multiple inverted images, and superposition eyes, which form

1001-451: A parabolic mirror to focus the image; it combines features of superposition and apposition eyes. Another kind of compound eye, found in males of Order Strepsiptera , employs a series of simple eyes—eyes having one opening that provides light for an entire image-forming retina. Several of these eyelets together form the strepsipteran compound eye, which is similar to the 'schizochroal' compound eyes of some trilobites . Because each eyelet

1078-420: A pit to reduce the angles of light that enters and affects the eye-spot, to allow the organism to deduce the angle of incoming light. Found in about 85% of phyla, these basic forms were probably the precursors to more advanced types of "simple eyes". They are small, comprising up to about 100 cells covering about 100 μm. The directionality can be improved by reducing the size of the aperture, by incorporating

1155-544: A plural form can pull double duty as the singular form (or vice versa), as has happened with the word "data" . The plural is used, as a rule, for quantities other than one (and other than those quantities represented by other grammatical numbers, such as dual, which a language may possess). Thus it is frequently used with numbers higher than one ( two cats , 101 dogs , four and a half hours ) and for unspecified amounts of countable things ( some men , several cakes , how many lumps? , birds have feathers ). The precise rules for

1232-631: A plural sense, as in the government are agreed . The reverse is also possible: the United States is a powerful country . See synesis , and also English plural § Singulars as plural and plurals as singular . In part-of-speech tagging notation, tags are used to distinguish different types of plurals based on their grammatical and semantic context. Resolution varies, for example the Penn-Treebank tagset (~36 tags) has two tags: NNS - noun, plural, and NPS - Proper noun, plural , while

1309-439: A plural when it means water from a particular source ( different waters make for different beers ) and in expressions like by the waters of Babylon . Certain collective nouns do not have a singular form and exist only in the plural, such as " clothes ". There are also nouns found exclusively or almost exclusively in the plural, such as the English scissors . These are referred to with the term plurale tantum . Occasionally,

1386-498: A reflective layer behind the receptor cells, or by filling the pit with a refractile material. Pit vipers have developed pits that function as eyes by sensing thermal infra-red radiation, in addition to their optical wavelength eyes like those of other vertebrates (see infrared sensing in snakes ). However, pit organs are fitted with receptors rather different from photoreceptors, namely a specific transient receptor potential channel (TRP channels) called TRPV1 . The main difference

1463-466: A refractive cornea: these have a negative lens, enlarging the observed image by up to 50% over the receptor cells, thus increasing their optical resolution. In the eyes of most mammals , birds , reptiles, and most other terrestrial vertebrates (along with spiders and some insect larvae) the vitreous fluid has a higher refractive index than the air. In general, the lens is not spherical. Spherical lenses produce spherical aberration. In refractive corneas,

1540-617: A resolution better than 1°. Also, superposition eyes can achieve greater sensitivity than apposition eyes , so are better suited to dark-dwelling creatures. Eyes also fall into two groups on the basis of their photoreceptor's cellular construction, with the photoreceptor cells either being ciliated (as in the vertebrates) or rhabdomeric . These two groups are not monophyletic; the Cnidaria also possess ciliated cells, and some gastropods and annelids possess both. Some organisms have photosensitive cells that do nothing but detect whether

1617-405: A sharp image. Ocelli (pit-type eyes of arthropods) blur the image across the whole retina, and are consequently excellent at responding to rapid changes in light intensity across the whole visual field; this fast response is further accelerated by the large nerve bundles which rush the information to the brain. Focusing the image would also cause the sun's image to be focused on a few receptors, with

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1694-499: A single erect image. Compound eyes are common in arthropods, annelids and some bivalved molluscs. Compound eyes in arthropods grow at their margins by the addition of new ommatidia. Apposition eyes are the most common form of eyes and are presumably the ancestral form of compound eyes. They are found in all arthropod groups, although they may have evolved more than once within this phylum. Some annelids and bivalves also have apposition eyes. They are also possessed by Limulus ,

1771-454: A single lens. Jumping spiders have one pair of large simple eyes with a narrow field of view , augmented by an array of smaller eyes for peripheral vision . Some insect larvae , like caterpillars , have a type of simple eye ( stemmata ) which usually provides only a rough image, but (as in sawfly larvae) can possess resolving powers of 4 degrees of arc, be polarization-sensitive, and capable of increasing its absolute sensitivity at night by

1848-408: A spherical lens, cornea and retina, but the vision is blurry. Heterogeneous eyes have evolved at least nine times: four or more times in gastropods , once in the copepods , once in the annelids , once in the cephalopods , and once in the chitons , which have aragonite lenses. No extant aquatic organisms possess homogeneous lenses; presumably the evolutionary pressure for a heterogeneous lens

1925-415: A transparent humour that optimised colour filtering, blocked harmful radiation, improved the eye's refractive index , and allowed functionality outside of water. The transparent protective cells eventually split into two layers, with circulatory fluid in between that allowed wider viewing angles and greater imaging resolution, and the thickness of the transparent layer gradually increased, in most species with

2002-408: A word may in fact have a number of plural forms, to allow for simultaneous agreement within other categories such as case , person and gender , as well as marking of categories belonging to the word itself (such as tense of verbs, degree of comparison of adjectives, etc.) Verbs often agree with their subject in number (as well as in person and sometimes gender). Examples of plural forms are

2079-400: Is a combination of inputs from the numerous ommatidia (individual "eye units"), which are located on a convex surface, thus pointing in slightly different directions. Compared with simple eyes, compound eyes possess a very large view angle, and can detect fast movement and, in some cases, the polarisation of light. Because the individual lenses are so small, the effects of diffraction impose

2156-412: Is a simple eye, it produces an inverted image; those images are combined in the brain to form one unified image. Because the aperture of an eyelet is larger than the facets of a compound eye, this arrangement allows vision under low light levels. Good fliers such as flies or honey bees, or prey-catching insects such as praying mantis or dragonflies , have specialised zones of ommatidia organised into

2233-404: Is advantageous to have a convex eye-spot, which gathers more light than a flat or concave one. This would have led to a somewhat different evolutionary trajectory for the vertebrate eye than for other animal eyes. The thin overgrowth of transparent cells over the eye's aperture, originally formed to prevent damage to the eyespot, allowed the segregated contents of the eye chamber to specialise into

2310-430: Is common in mammals, including humans. The simplest eyes are pit eyes. They are eye-spots which may be set into a pit to reduce the angle of light that enters and affects the eye-spot, to allow the organism to deduce the angle of incoming light. Eyes enable several photo response functions that are independent of vision. In an organism that has more complex eyes, retinal photosensitive ganglion cells send signals along

2387-542: Is considered a key factor in this. The majority of the advancements in early eyes are believed to have taken only a few million years to develop, since the first predator to gain true imaging would have touched off an "arms race" among all species that did not flee the photopic environment. Prey animals and competing predators alike would be at a distinct disadvantage without such capabilities and would be less likely to survive and reproduce. Hence multiple eye types and subtypes developed in parallel (except those of groups, such as

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2464-401: Is great enough for this stage to be quickly "outgrown". This eye creates an image that is sharp enough that motion of the eye can cause significant blurring. To minimise the effect of eye motion while the animal moves, most such eyes have stabilising eye muscles. The ocelli of insects bear a simple lens, but their focal point usually lies behind the retina; consequently, those can not form

2541-410: Is little difference in refractive index between the vitreous fluid and the surrounding water. Hence creatures that have returned to the water—penguins and seals, for example—lose their highly curved cornea and return to lens-based vision. An alternative solution, borne by some divers, is to have a very strongly focusing cornea. A unique feature of most mammal eyes is the presence of eyelids which wipe

2618-413: Is part of an organism's visual system . In higher organisms, the eye is a complex optical system that collects light from the surrounding environment, regulates its intensity through a diaphragm , focuses it through an adjustable assembly of lenses to form an image , converts this image into a set of electrical signals, and transmits these signals to the brain through neural pathways that connect

2695-472: Is that photoreceptors are G-protein coupled receptors but TRP are ion channels . The resolution of pit eyes can be greatly improved by incorporating a material with a higher refractive index to form a lens, which may greatly reduce the blur radius encountered—hence increasing the resolution obtainable. The most basic form, seen in some gastropods and annelids, consists of a lens of one refractive index. A far sharper image can be obtained using materials with

2772-579: Is used after zéro . English also tends to use the plural with decimal fractions , even if less than one, as in 0.3 metres , 0.9 children . Common fractions less than one tend to be used with singular expressions: half (of) a loaf , two-thirds of a mile . Negative numbers are usually treated the same as the corresponding positive ones: minus one degree , minus two degrees . Again, rules on such matters differ between languages. In some languages, including English, expressions that appear to be singular in form may be treated as plural if they are used with

2849-597: The French mangeons, mangez, mangent – respectively the first-, second- and third-person plural of the present tense of the verb manger . In English a distinction is made in the third person between forms such as eats (singular) and eat (plural). Adjectives may agree with the noun they modify; examples of plural forms are the French petits and petites (the masculine plural and feminine plural respectively of petit ). The same applies to some determiners – examples are

2926-442: The arthropods are composed of many simple facets which, depending on anatomical detail, may give either a single pixelated image or multiple images per eye. Each sensor has its own lens and photosensitive cell(s). Some eyes have up to 28,000 such sensors arranged hexagonally, which can give a full 360° field of vision. Compound eyes are very sensitive to motion. Some arthropods, including many Strepsiptera , have compound eyes of only

3003-440: The copepod Pontella has three. The outer has a parabolic surface, countering the effects of spherical aberration while allowing a sharp image to be formed. Another copepod, Copilia , has two lenses in each eye, arranged like those in a telescope. Such arrangements are rare and poorly understood, but represent an alternative construction. Multiple lenses are seen in some hunters such as eagles and jumping spiders, which have

3080-420: The incident light , while those to one side reflect it. There are some exceptions from the types mentioned above. Some insects have a so-called single lens compound eye, a transitional type which is something between a superposition type of the multi-lens compound eye and the single lens eye found in animals with simple eyes. Then there is the mysid shrimp, Dioptromysis paucispinosa . The shrimp has an eye of

3157-414: The retinohypothalamic tract to the suprachiasmatic nuclei to effect circadian adjustment and to the pretectal area to control the pupillary light reflex . Complex eyes distinguish shapes and colours . The visual fields of many organisms, especially predators, involve large areas of binocular vision for depth perception . In other organisms, particularly prey animals, eyes are located to maximise

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3234-472: The CLAWS 7 tagset (~149 tags) uses six: NN2 - plural common noun, NNL2 - plural locative noun, NNO2 - numeral noun, plural, NNT2 - temporal noun, plural, NNU2 - plural unit of measurement, NP2 - plural proper noun. Eye An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It

3311-434: The French plural definite article les , and the English demonstratives these and those . It is common for pronouns , particularly personal pronouns , to have distinct plural forms. Examples in English are we ( us , etc.) and they ( them etc.; see English personal pronouns ), and again these and those (when used as demonstrative pronouns ). In Welsh, a number of common prepositions also inflect to agree with

3388-702: The Middle Ages and it is also the Romanian equivalent to the Slavic Hospodar . Moldavian and Wallachian rulers had used this term for their title of authority as the head of state, while " voievod " represented the military rank as the head of the army. The title acquired an officially recognized meaning after Moldavia and Wallachia united to form the Romanian United Principalities under Alexander John I , who had become

3465-501: The addition of affixes , like the English -(e)s and -ies suffixes , or ablaut , as in the derivation of the plural geese from goose , or a combination of the two. Some languages may also form plurals by reduplication , but not as productively. It may be that some nouns are not marked for plural at all, like sheep and series in English. In languages which also have a case system, such as Latin and Russian , nouns can have not just one plural form but several, corresponding to

3542-399: The cells of the dilator muscle. The vitreous is the transparent, colourless, gelatinous mass that fills the space between the lens of the eye and the retina lining the back of the eye. It is produced by certain retinal cells. It is of rather similar composition to the cornea, but contains very few cells (mostly phagocytes which remove unwanted cellular debris in the visual field, as well as

3619-399: The directionality of light by the shadow cast by its opaque body. The ciliary body is triangular in horizontal section and is coated by a double layer, the ciliary epithelium. The inner layer is transparent and covers the vitreous body, and is continuous from the neural tissue of the retina. The outer layer is highly pigmented, continuous with the retinal pigment epithelium, and constitutes

3696-558: The dual and paucal can be found in some Slavic and Baltic languages (apart from those that preserve the dual number, such as Slovene ). These are known as "pseudo-dual" and "pseudo-paucal" grammatical numbers. For example, Polish and Russian use different forms of nouns with the numerals 2, 3, or 4 (and higher numbers ending with these ) than with the numerals 5, 6, etc. (genitive singular in Russian and nominative plural in Polish in

3773-588: The edge of its shell. It detects moving objects as they pass successive lenses. There is at least one vertebrate, the spookfish , whose eyes include reflective optics for focusing of light. Each of the two eyes of a spookfish collects light from both above and below; the light coming from above is focused by a lens, while that coming from below, by a curved mirror composed of many layers of small reflective plates made of guanine crystals . A compound eye may consist of thousands of individual photoreceptor units or ommatidia ( ommatidium , singular). The image perceived

3850-422: The eye allows light to enter and project onto a light-sensitive layer of cells known as the retina . The cone cells (for colour) and the rod cells (for low-light contrasts) in the retina detect and convert light into neural signals which are transmitted to the brain via the optic nerve to produce vision. Such eyes are typically spheroid, filled with the transparent gel-like vitreous humour , possess

3927-412: The eye and spread tears across the cornea to prevent dehydration. These eyelids are also supplemented by the presence of eyelashes , multiple rows of highly innervated and sensitive hairs which grow from the eyelid margins to protect the eye from fine particles and small irritants such as insects. An alternative to a lens is to line the inside of the eye with "mirrors", and reflect the image to focus at

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4004-428: The eye via the optic nerve to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, classified into compound eyes and non-compound eyes. Compound eyes are made up of multiple small visual units, and are common on insects and crustaceans . Non-compound eyes have a single lens and focus light onto the retina to form a single image. This type of eye

4081-450: The eye. Photoreception is phylogenetically very old, with various theories of phylogenesis. The common origin ( monophyly ) of all animal eyes is now widely accepted as fact. This is based upon the shared genetic features of all eyes; that is, all modern eyes, varied as they are, have their origins in a proto-eye believed to have evolved some 650-600 million years ago, and the PAX6 gene

4158-490: The field of view, such as in rabbits and horses , which have monocular vision . The first proto-eyes evolved among animals 600  million years ago about the time of the Cambrian explosion . The last common ancestor of animals possessed the biochemical toolkit necessary for vision, and more advanced eyes have evolved in 96% of animal species in six of the ~35 main phyla . In most vertebrates and some molluscs ,

4235-430: The former case, genitive plural in the latter case). Also some nouns may follow different declension patterns when denoting objects which are typically referred to in pairs. For example, in Polish, the noun " oko ", among other meanings, may refer to a human or animal eye or to a drop of oil on water. The plural of " oko " in the first meaning is " oczy " (even if actually referring to more than two eyes), while in

4312-481: The geometry of cephalopod and most vertebrate eyes creates the impression that the vertebrate eye evolved from an imaging cephalopod eye , but this is not the case, as the reversed roles of their respective ciliary and rhabdomeric opsin classes and different lens crystallins show. The very earliest "eyes", called eye-spots, were simple patches of photoreceptor protein in unicellular animals. In multicellular beings, multicellular eyespots evolved, physically similar to

4389-449: The horseshoe crab, and there are suggestions that other chelicerates developed their simple eyes by reduction from a compound starting point. (Some caterpillars appear to have evolved compound eyes from simple eyes in the opposite fashion.) Apposition eyes work by gathering a number of images, one from each eye, and combining them in the brain, with each eye typically contributing a single point of information. The typical apposition eye has

4466-561: The hot vents, allowing the creatures to avoid being boiled alive. There are ten different eye layouts. Eye types can be categorised into "simple eyes", with one concave photoreceptive surface, and "compound eyes", which comprise a number of individual lenses laid out on a convex surface. "Simple" does not imply a reduced level of complexity or acuity. Indeed, any eye type can be adapted for almost any behaviour or environment. The only limitations specific to eye types are that of resolution—the physics of compound eyes prevents them from achieving

4543-425: The hyalocytes of Balazs of the surface of the vitreous, which reprocess the hyaluronic acid ), no blood vessels, and 98–99% of its volume is water (as opposed to 75% in the cornea) with salts, sugars, vitrosin (a type of collagen), a network of collagen type II fibres with the mucopolysaccharide hyaluronic acid, and also a wide array of proteins in micro amounts. Amazingly, with so little solid matter, it tautly holds

4620-708: The lemma form, sometimes combining it with an additional vowel. (In French, however, this plural suffix is often not pronounced.) This construction is also found in German and Dutch, but only in some nouns. Suffixing is cross-linguistically the most common method of forming plurals. In Welsh , the reference form, or default quantity, of some nouns is plural, and the singular form is formed from it, e.g., llygod , mice -> llygoden , mouse; erfin , turnips -> erfinen , turnip. In many languages, words other than nouns may take plural forms, these being used by way of grammatical agreement with plural nouns (or noun phrases ). Such

4697-424: The lens tissue is corrected with inhomogeneous lens material (see Luneburg lens ), or with an aspheric shape. Flattening the lens has a disadvantage; the quality of vision is diminished away from the main line of focus. Thus, animals that have evolved with a wide field-of-view often have eyes that make use of an inhomogeneous lens. As mentioned above, a refractive cornea is only useful out of water. In water, there

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4774-777: The number of their associated nouns. Some languages also have a dual (denoting exactly two of something) or other systems of number categories. However, in English and many other languages, singular and plural are the only grammatical numbers, except for possible remnants of dual number in pronouns such as both and either . In many languages, there is also a dual number (used for indicating two objects). Some other grammatical numbers present in various languages include trial (for three objects) and paucal (for an imprecise but small number of objects). In languages with dual, trial, or paucal numbers, plural refers to numbers higher than those. However, numbers besides singular, plural, and (to

4851-411: The number, person, and sometimes gender of the noun or pronoun they govern. Certain nouns do not form plurals. A large class of such nouns in many languages is that of uncountable nouns , representing mass or abstract concepts such as air , information , physics . However, many nouns of this type also have countable meanings or other contexts in which a plural can be used; for example water can take

4928-459: The parabolic superposition compound eye type, seen in arthropods such as mayflies , the parabolic surfaces of the inside of each facet focus light from a reflector to a sensor array. Long-bodied decapod crustaceans such as shrimp , prawns , crayfish and lobsters are alone in having reflecting superposition eyes, which also have a transparent gap but use corner mirrors instead of lenses. This eye type functions by refracting light, then using

5005-451: The paucal, the plural, and the greater plural is often relative to the type of object under discussion. For example, in discussing oranges, the paucal number might imply fewer than ten, whereas for the population of a country, it might be used for a few hundred thousand. The Austronesian languages of Sursurunga and Lihir have extremely complex grammatical number systems, with singular, dual, paucal, greater paucal, and plural. Traces of

5082-461: The possibility of damage under the intense light; shielding the receptors would block out some light and thus reduce their sensitivity. This fast response has led to suggestions that the ocelli of insects are used mainly in flight, because they can be used to detect sudden changes in which way is up (because light, especially UV light which is absorbed by vegetation, usually comes from above). Some marine organisms bear more than one lens; for instance

5159-483: The pseudo-dual as plural of "eyes" עין / עינים ‎ ʿạyin / ʿēnạyim "eye / eyes" as well as "hands", "legs" and several other words are retained. For further information, see Dual (grammatical number) § Hebrew . Certain nouns in some languages have the unmarked form referring to multiple items, with an inflected form referring to a single item. These cases are described with the terms collective number and singulative number . Some languages may possess

5236-438: The receptor patches for taste and smell. These eyespots could only sense ambient brightness: they could distinguish light and dark, but not the direction of the light source. Through gradual change, the eye-spots of species living in well-lit environments depressed into a shallow "cup" shape. The ability to slightly discriminate directional brightness was achieved by using the angle at which the light hit certain cells to identify

5313-514: The refracting superposition type, in the rear behind this in each eye there is a single large facet that is three times in diameter the others in the eye and behind this is an enlarged crystalline cone. This projects an upright image on a specialised retina. The resulting eye is a mixture of a simple eye within a compound eye. Another version is a compound eye often referred to as "pseudofaceted", as seen in Scutigera . This type of eye consists of

5390-641: The ruler of both states since 1859. Alexander John abdicated in 1866 and was succeeded by Carol I , who promulgated the first constitution who officially used the name Romania for the country. He held the title until 1881. When Romania was proclaimed a kingdom in March 1881, Carol became its first king. This is a graphical lifespan timeline of Domnitors of Romania. The domnitors are listed in order of office. Plural Words of other types, such as verbs , adjectives and pronouns , also frequently have distinct plural forms, which are used in agreement with

5467-416: The same angle on the other side. The result is an image at half the radius of the eye, which is where the tips of the rhabdoms are. This type of compound eye, for which a minimal size exists below which effective superposition cannot occur, is normally found in nocturnal insects, because it can create images up to 1000 times brighter than equivalent apposition eyes, though at the cost of reduced resolution. In

5544-573: The second it is " oka " (even if actually referring to exactly two drops). Traces of dual can also be found in Modern Hebrew . Biblical Hebrew had grammatical dual via the suffix -ạyim as opposed to ־ים ‎ -īm for masculine words . Contemporary use of a true dual number in Hebrew is chiefly used in words regarding time and numbers. However, in Biblical and Modern Hebrew,

5621-404: The source. The pit deepened over time, the opening diminished in size, and the number of photoreceptor cells increased, forming an effective pinhole camera that was capable of dimly distinguishing shapes. However, the ancestors of modern hagfish , thought to be the protovertebrate, were evidently pushed to very deep, dark waters, where they were less vulnerable to sighted predators, and where it

5698-622: The surroundings are light or dark , which is sufficient for the entrainment of circadian rhythms . These are not considered eyes because they lack enough structure to be considered an organ, and do not produce an image. Every technological method of capturing an optical image that humans commonly use occurs in nature, with the exception of zoom and Fresnel lenses . Simple eyes are rather ubiquitous, and lens-bearing eyes have evolved at least seven times in vertebrates , cephalopods , annelids , crustaceans and Cubozoa . Pit eyes, also known as stemmata , are eye-spots which may be set into

5775-399: The use of plurals, however, depends on the language – for example Russian uses the genitive singular rather than the plural after certain numbers (see above). Treatments differ in expressions of zero quantity: English often uses the plural in such expressions as no injuries and zero points , although no (and zero in some contexts) may also take a singular. In French, the singular form

5852-481: The various cases. The inflection might affect multiple words, not just the noun; the noun itself need not become plural as such, with other parts of the expression indicating the plurality. In English, the most common formation of plural nouns is by adding an - s suffix to the singular noun. (For details and different cases, see English plurals .) Just like in English, noun plurals in French, Spanish, and Portuguese are also typically formed by adding an -s suffix to

5929-469: The vertebrates, that were only forced into the photopic environment at a late stage). Eyes in various animals show adaptation to their requirements. For example, the eye of a bird of prey has much greater visual acuity than a human eye , and in some cases can detect ultraviolet radiation. The different forms of eye in, for example, vertebrates and molluscs are examples of parallel evolution , despite their distant common ancestry. Phenotypic convergence of

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