Fish

Fish come in many shapes and sizes. This is a sea dragon (kira), a close relative of the seahorse. They are camouflaged as floating seaweed.[1][2]
Dunkleosteus, a giant armoured arthrodire of the later Devonian. Up to 6 metres long, it lived in the Inland seas of North America.[3]
This is one of the first works of art: a sculpture of a fish; age:about 40.000 years.

Fish (plural: fish or fishes) are vertebrates which live in water and respire (get oxygen) with gills. They lack limbs with digits (fingers & toes). This is a definition which does not quite work: some amphibia also live in water and have external gills, but they are not fishes.

Fish used to be a class of vertebrates. Now the term covers five classes of aquatic vertebrates:

Jawless fish
Armoured fish
Cartilaginous fish
Ray-finned fish
Lobe-finned fish

There are more fish than tetrapods (land vertebrates): there are over 33,000 described species of fish.[4] Fish are usually covered with scales. They have two sets of paired fins and several unpaired fins. Most fish are cold-blooded (poikilotherm). A fish takes in the oxygen from the water using gills. There are many different kinds of fish. They live in fresh water in lakes and rivers, and in salt water in the ocean. Some fish are less than one centimeter long. The largest fish is the whale shark, which can be almost 15 meters long and weigh 15 tons. Most fish live in the water. A group of fish called the lungfish have developed lungs because they live in rivers and pools which dry up in certain parts of the year. They burrow into mud and aestivate until the water returns.

'Fish' is a paraphyletic term in cladistics because it lacks a monophyletic group of descendants. It does not include the land vertebrates or tetrapods, which descended from fish.

Fish or fishes?

Though often used interchangeably, these words have different meanings. Fish is used either as singular noun or to describe a group of specimens from a single species. Fishes describes a group of different species.[5]

Other Languages
Acèh: Eungkôt
Afrikaans: Vis
Alemannisch: Fische
አማርኛ: ዓሣ
Ænglisc: Fisc
Аҧсшәа: Аҧсыӡ
العربية: سمك
aragonés: Pisces
armãneashti: Pescu
অসমীয়া: মাছ
asturianu: Pexe
Atikamekw: Names
Avañe'ẽ: Pira
Aymar aru: Challwa
azərbaycanca: Balıqlar
تۆرکجه: بالیقلار
বাংলা: মাছ
Bahasa Banjar: Iwak
Bân-lâm-gú:
башҡортса: Балыҡтар
беларуская: Рыбы
беларуская (тарашкевіца)‎: Рыбы
Bislama: Fis
български: Риба
Boarisch: Fiisch
བོད་ཡིག: ཉ།
bosanski: Ribe
brezhoneg: Pesk
буряад: Загаһан
català: Peix
Чӑвашла: Пулă
Cebuano: Isda
chiShona: Hove
Cymraeg: Pysgodyn
dansk: Fisk
Deutsch: Fische
dolnoserbski: Ryby
eesti: Kalad
Ελληνικά: Ψάρι
English: Fish
эрзянь: Калт
español: Pez
Esperanto: Fiŝoj
euskara: Arrain
فارسی: ماهی
Fiji Hindi: Machhri
føroyskt: Fiskur
français: Poisson
Frysk: Fisken
Gaeilge: Iasc
Gaelg: Eeast
Gàidhlig: Iasg
galego: Peixes
贛語:
ગુજરાતી: માછલી
客家語/Hak-kâ-ngî: Ǹg-è
хальмг: Заһсн
한국어: 물고기
Hausa: Kifi
Հայերեն: Ձկներ
हिन्दी: मछली
hornjoserbsce: Ryby
hrvatski: Ribe
Ido: Fisho
Ilokano: Ikan
Bahasa Indonesia: Ikan
interlingua: Pisce
ᐃᓄᒃᑎᑐᑦ/inuktitut: ᐃᖃᓗᒃ
Iñupiak: Iqaluk
Ирон: Кæсæгтæ
isiXhosa: Intlanzi
íslenska: Fiskur
italiano: Pesce
עברית: דג
Basa Jawa: Iwak
ಕನ್ನಡ: ಮೀನು
Kapampangan: Asan
ქართული: თევზები
kaszëbsczi: Rëbë
қазақша: Балықтар
kernowek: Pysk
Kiswahili: Samaki
коми: Чери
Kreyòl ayisyen: Pwason
kurdî: Masî
Кыргызча: Балыктар
кырык мары: Кол
Ladino: Pishkados
лакку: Чавахъ
Latina: Piscis
latviešu: Zivis
Lëtzebuergesch: Fësch
lietuvių: Žuvys
Limburgs: Vèsse
lingála: Mbísi
la .lojban.: finpe
lumbaart: Pès
magyar: Halak
македонски: Риби
Malagasy: Hazandrano
മലയാളം: മത്സ്യം
मराठी: मासा
მარგალური: ჩხომი
مصرى: سمك
Bahasa Melayu: Ikan
Baso Minangkabau: Ikan
Mìng-dĕ̤ng-ngṳ̄: Ngṳ̀
монгол: Загас
မြန်မာဘာသာ: ငါး (တိရစ္ဆာန်)
Nāhuatl: Michin
Dorerin Naoero: Iy
Na Vosa Vakaviti: Ika
Nederlands: Vissen (dieren)
Nedersaksies: Visk
Nēhiyawēwin / ᓀᐦᐃᔭᐍᐏᐣ: ᓇᒣᔅ
नेपाली: माछा
नेपाल भाषा: न्या
日本語: 魚類
Napulitano: Pisce
Nordfriisk: Fasker
norsk: Fisk
norsk nynorsk: Fisk
Nouormand: Paîsson
occitan: Peis
олык марий: Кол
ଓଡ଼ିଆ: ମାଛ
oʻzbekcha/ўзбекча: Baliqlar
ਪੰਜਾਬੀ: ਮੱਛੀ
پنجابی: مچھی
Patois: Fish
Picard: Pichon
Plattdüütsch: Fisch
polski: Ryby
português: Peixe
Qaraqalpaqsha: Balıq
qırımtatarca: Balıq
Ripoarisch: Fesch
română: Pește
Runa Simi: Challwa
русиньскый: Рыбы
русский: Рыбы
саха тыла: Балык
संस्कृतम्: मत्स्याः
Scots: Fish
shqip: Peshqit
sicilianu: Pisci
සිංහල: මාළු
سنڌي: مڇي
slovenščina: Ribe
ślůnski: Ryby
Soomaaliga: Malaay
کوردی: ماسی
Sranantongo: Fisi
српски / srpski: Рибе
srpskohrvatski / српскохрватски: Riba
Basa Sunda: Lauk
suomi: Kala
svenska: Fiskar
Tagalog: Isda
தமிழ்: மீன்
татарча/tatarça: Балыклар
తెలుగు: చేప
ไทย: ปลา
тоҷикӣ: Моҳӣ
ᏣᎳᎩ: ᎠᏣᏗ
ತುಳು: ಮೀನ್
Türkçe: Balık
удмурт: Чорыг
українська: Риби
اردو: مچھلی
Vahcuengh: Duzbya
vèneto: Pesi
vepsän kel’: Kalad
Tiếng Việt:
Võro: Kala
walon: Pexhon
文言:
West-Vlams: Visschn
Winaray: Isda
吴语:
ייִדיש: פיש
粵語:
Zazaki: Mase
žemaitėška: Žovis
中文:
Bahasa Hulontalo: Uponula
ГӀалгӀай: Чкъаьрий
Kabɩyɛ: Kpakpayaɣ
Lingua Franca Nova: Pex