Words for four and related things in Celtic languages:
| Proto-Celtic | *kʷetwares = four *kʷetwariyos = fourth |
|---|---|
| Gaulish | petru, petuar = four petuarios = fourth |
| Old Irish (Goídelc) | cethair [ˈkʲeθirʲ] = four cethramad [ˈkʲeθraṽað] = fourth cethracha = forty cethrar = four people cethardúil = four elements |
| Middle Irish (Gaoidhealg) | cethair = four cethramad = fourth cethrar = four people cethracha = forty cetharchair = four-sided, square, rectangular cethairríad = four-wheeled chariot or carriage cethardenus = space of four days cethardóit = group of four cetharaird = the four points of the compass, the four quarters, the world, universe |
| Irish (Gaeilge) | ceathair [ˈcahəɾʲ/ˈcæɾʲ] = four, quadruped ceithre [ˈcɛɾʲə/ˈçɛɾʲə] = four ceathrar [ˈcahɾˠəɾˠ/cæːɾˠ] = four people ceathracha = forty ceathrú [cahˈɾˠuː] = quarter, thigh, quatrain ceathrúnach = quartermaster ceathairbhliantúil = quadrennial ceathairchodach = fourfold, quadruple ceathairchosach = fourfooted, quadruped ceathairéad = quartet ceathairfhillte = quarto, fourfold |
| Scottish Gaelic (Gàidhlig) | ceithir [kʲehɪrʲ] = four ceathramh [kʲɛrəv] (4mh) fourth (4th) ceathrar [kʲɛrər] = four (people) ceathrad [kʲɛrəd] = forty cairteal [kar̪ˠʃdʲal] = quarter; quarters, lodgings ceithir-chasach = quadruped, four-legged animal ceithir-cheàrnach = quadrilateral ceithir-fillte = quadruple, fourfold, four-ply |
| Manx (Gaelg) | kiare [kʲeːə(r)] = four, foursome, quartet kiarroo, (yn) chiarroo = (the) fourth kerroo = fourth, quarter, quatrain kiarad = forty kiare-fillagh, kiare-filley = fourfold, quadruple kiare-lhiatteeagh, kiare-lhiatteean = four-sided, quadrilateral kiare-chassagh = four-footed, four-legged, quadruped |
| Proto-Brythonic | *pedwar [pɛdˈwaːr] = four *pėdwėrɨð [pe̝dwe̝ˈrˑɨːð] = fourth |
| Old Welsh | petguar = four petguaret = fourth |
| Middle Welsh (Kymraec) | pedwar, peduar = four (m) pedeyr, pedair, pedeir = four (f) pedweryd = fourth (m) pedwyred = fourth (m) pedwar deg, pedeir deg = fourteen pedwar/pedeir ar bymthec = nineteen pedwar ugein(t) = eighty |
| Welsh (Cymraeg) | pedwar [ˈpɛdwar] = four (m) pedair [ˈpɛdai̯r/ˈpeːdai̯r] = four (f) pedwerydd [pɛdˈwɛrɨ̞ð] (4ydd) = fourth (m) pedwaredd [pɛdˈwarɛð] (4edd) = fourth (f) pedwarplyg = quadruple pedwaraf, pedwaru = to divide into four, quarter pedwaraid = set of four, foursome pedwar ar ddeg = fourteen pedwar ar bymtheg = nineteen pedwar deg = forty pedwar ugain = eighty |
| Middle Cornish (Cernewec) | peswar = four (m) pedar = four (f) peswere, pyswere = fourth peswardhec, pazawardhak = fourteen padzhar iganz = eighty padzhar iganz ha deg = ninety |
| Cornish (Kernewek) | peswar, pajar = four (m) peder = four (f) peswora, pajwora = fourth peswartrosek = fourfooted peswardhek = fourteen peswar ugens = eighty |
| Old Breton | petguar = four petguare = fourth |
| Middle Breton (Brezonec) | peuar, puar = four peuare, pevare = fourth peuarzec, pévarzecq, piarzeg = fourteen peuaruguent, pêver huguent, pévar uguent = eighty pevar-benveg = quartet pevarc’hartier = to cut in quarters pévar c’hemend = quadruple pevar(-)c’hementi(ñ) = to quadruple |
| Breton (Brezhoneg) | pevar = four (m) peder = four (f) pevare = fourth pevarved = fourth (m) pedervet = fourth (f) pevarzek = fourteen pevar-ugent = eighty pevarad = quartet pevarzuek = quadrilatéral |
Etymology: from Proto-Indo-European *kʷetwóres (four) and *kʷetwr̥yós (fourth) [source].
English words from the same roots include four, quarter, quart, quartet, quaruple, and words beginning with tetra-, such as tetradecimal (a 14-base counting system) [source].
Sources: Wiktionary, Am Faclair Beag, Online Manx Dictionary, Teanglann.ie, eDIL – Electronic Dictionary of the Irish Language, In Dúil Bélrai English – Old Irish glossary, Geiriadur Prifysgol Cymru, Gerlyver Kernewek, Gerlyvyr Cernewec, Dictionaire Favereau, TermOfis, Le dictionnaire diachronique du breton, Geriafurch, English – ProtoCeltic WordList (PDF), Etymological Dictionary Of Proto Celtic