Irish orthography is theset of conventions used to write theIrish language. Aspelling reform in the mid-20th century led toAn Caighdeán Oifigiúil, the modernstandardwritten form used by theGovernment of Ireland, which regulates bothspelling andgrammar.^[1] The reform removed inter-dialectalsilent letters, simplified someletter sequences, and modernised archaic spellings to reflect modern pronunciation, but it also removed letters pronounced in some dialects but not in others.

Irish spelling represents all Irishdialects to a high degree despite their considerable phonological variation, e.g.crann ("tree") is read/kɾˠan̪ˠ/ in Mayo andUlster,/kɾˠaːn̪ˠ/ in Galway, or/kɾˠəun̪ˠ/ inMunster. Some words may have dialectal pronunciations not reflected by their standard spelling, and they sometimes have distinct dialectal spellings to reflect this.^[2][3]

Latin script has been thewriting system used to write Irish since the 5th century, when it replacedOgham, which was used to writePrimitive Irish andOld Irish.^[4] Prior to the mid-20th century,Gaelic type (cló Gaelach) was the maintypeface used to write Irish; now, it is usually replaced byRoman type (cló Rómhánach). The use of Ogham and Gaelic type today is restricted to decorative or self-consciously traditional contexts. Thedot above alenited letter in Gaelic type is usually replaced by a following⟨h⟩ in Roman type (e.g.⟨ċ⟩ →⟨ch⟩).^[5]

The traditional Irishalphabet (aibítir) consists of 18 letters:⟨a, b, c, d, e, f, g, h, i, l, m, n, o, p, r, s, t, u⟩. It does not contain⟨j, k, q, v, w, x, y, z⟩, although they are used in scientific terminology and modernloanwords.⟨v⟩ occurs in a small number of (mainlyonomatopoeic) native words (e.g.vácarnach "to quack" andvrác "caw") andcolloquialisms (e.g.víog forbíog "chirp" andvís forbís "screw").^[6]⟨h⟩, when notprefixed to a word initial vowel or after a consonant to showlenition, primarily occurs word initially in loanwords, e.g.hata "hat".⟨k⟩ is the only letter not listed byÓ Dónaill.

Vowels may beaccented with anacute accent (⟨á, é, í, ó, ú⟩; seebelow).^[7] Accented letters are considered variants of their unaccented equivalent, and they follow their unaccented equivalents in dictionaries (i.e.a,á…abhac,ábhacht,abhaile...).

English letter names are generally used in both colloquial and formal speech but there are modern Irish letter names (based on the originalLatin names), similar to other languages that use aLatin script alphabet. Tree names were historically used to name the letters. Tradition taught that they all derived from thenames of Ogham letters, though it is now known that only some of the earliest were named after trees.

Ingrapheme tophoneme correspondence tables on this page:

• "U" stands for Mayo and Ulster Irish, "C" for southern Connacht Irish, and "M" for Munster Irish.
• Initially and finally mean word initial or final unless stated otherwise.
• /∅/ means silent, i.e. that theletter(s) are not pronounced.
• TheIPA transcriptions of examples on this page are inConnacht Irish.

SeeIrish phonology for an explanation of the symbols used andIrish initial mutations for an explanation of eclipsis and lenition.

Consonants are generally "broad" (velarised) when beside⟨a, á, o, ó, u, ú⟩ and "slender" (palatalised) when beside⟨e, é, i, í⟩.^[3][11][12] Irish orthography does not allow consonant letters or digraphs to bedoubled (except in⟨ll, nn, rr⟩); in compound words which would result in doubled consonants, they are broken up by a hyphen (see below).

Vowel sequences are common in Irish spelling due to the "caol le caol agus leathan le leathan" ("slender with slender and broad with broad") rule, i.e. that the vowels on either side of any consonant (orconsonant cluster) must be both slender (⟨e, é, i, í⟩) or both broad (⟨a, á, o, ó, u, ú⟩), to unambiguously determine if the consonant(s) are broad or slender. An apparent exception is⟨ae⟩, which is followed by a broad consonant despite the⟨e⟩.^{[11][12][13][5]}

The pronunciation of vowels in Irish is mostly predictable from the following rules:

• Unstressed short vowels are generally reduced to/ə/.
• ⟨e⟩ before⟨a⟩ or⟨o⟩ and⟨i⟩ bordering either side of⟨u⟩ are silent, but mark a slender sonsonant. This is true for both long and short vowels.
• ⟨io, oi, ui⟩ have multiple pronunciations that depend on adjacent consonants.
• Accented vowels (⟨á, é, í, ó, ú⟩) representlong vowels and indigraphs andtrigraphs containing them, surrounding unaccented vowels are silent, but there are several exceptions, e.g. when preceded by two unaccented vowels.
• Accented vowels in succession are both pronounced, e.g.séú/ˈʃeːuː/ "sixth",ríúil/ˈɾˠiːuːlʲ/ "royal, kingly, majestic",báíocht/ˈbˠaːiːxt̪ˠ/ "sympathy", etc.
• ⟨i⟩ and⟨u⟩ are long before⟨á, ó⟩, e.g.fiáin/ˈfʲiːaːnʲ/ "wild",ruóg/ˈɾˠuːoːɡ/ "twine"
• A following⟨rd, rl, rn, rr⟩ lengthens some vowels and in Munster and Connacht. ⟨rr⟩ rarely ever occurs after a vowel other than ⟨a⟩.
• A following syllable-final⟨ll, nn⟩ or word-final⟨m, ng⟩ may lengthen or diphthongise some vowels depending on dialect.

When followed by⟨bh, dh, gh, mh⟩, a short vowel usually forms adiphthong or lengthens. In most dialects, this diphthong or lengthened vowel carries over to a neighbouring unstressed vowel.

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After ashort vowel, an unwrittenepenthetic/ə/ gets inserted between⟨l, n, r⟩ +⟨b, bh, ch, f, g, mh⟩ (as well as⟨p⟩, when derived from devoiced⟨b, bh, mh⟩), when within amorpheme boundary, e.g.gorm/ˈɡɔɾˠəmˠ/ "blue",dearg/ˈdʲaɾˠəɡ/ "red",dorcha/ˈd̪ˠɔɾˠəxə/ "dark",ainm/ˈanʲəmʲ/ "name",deilgneach/ˈdʲɛlʲəɟnʲəx/ "prickly, thorny"’leanbh/ˈl̠ʲanˠəw/ "child",airgead/ˈaɾʲəɟəd̪ˠ/ "silver, money". The main exception to this is⟨ng⟩ which is mainly used for/ŋ/ or/ɲ/.

Epenthesis does not occur afterlong vowels and diphthongs, e.g.téarma/tʲeːɾˠmˠə/ "term" ordualgas/ˈd̪ˠuəlˠɡəsˠ/ "duty", or acrossmorpheme boundaries (i.e. after prefixes and in compound words), e.g.garmhac/ˈɡaɾˠwak/ "grandson" (fromgar- "close, near" +mac "son"),an-chiúin/ˈan̪ˠçuːnʲ/ "very quiet" (froman- "very" +ciúin "quiet"),carrbhealach/ˈkaːɾˠvʲalˠəx/ "carriageway, roadway" (fromcarr "car" +bealach "way, road").

In Munster, epenthesis also occurs across morpheme boundaries, when⟨l, n, r⟩ follow⟨b, bh, ch, g, mh⟩ (after any vowel) or⟨th⟩ (after short vowels), and when⟨n⟩ follows⟨c, g, m, r⟩.

Inverb forms some letters and letter combinations are pronounced differently from elsewhere:

Outside of verbs suffixes, the following words are pronounced irregularly for their spelling:

• ⟨ai⟩ is pronounced/ɛ/ in the following words:daibhir "poor",raibh "to be (presentsubjunctive or pastdependent)", andsaibhir "rich".
• The prepositionag "at", is pronounced/ɛg/, as if spelled ⟨oig⟩. This carries over into inflected formsaige "at him" andaici "at her".
  • When used as a particle indicatingprogressive verbs,ag is pronounced regularly as/əg/.
• The preposositionar "on" is pronounced/ɛɾ/, as if spelled ⟨oir⟩. Its inflected formsair " on him" anduirthi "on her" are pronounced/ɛɾʲ/ and/ɔɾˠhi/, respectively.
• beag "small" is pronounced/bʲɔg/, as if part of the group below.
• ⟨eo⟩ is pronounced/ʲɔ/ in four words:anseo "here"/ən̠ʲˈʃɔ/,deoch "drink"/dʲɔx/,eochair "key"/(ʲ)ɔxəɾʲ/, andseo "this"/ʃɔ/, using a short vowel.
• féin "self" is often pronounced/heːnʲ/, as if spelled ⟨héin⟩.

An Caighdeán Oifigiúil currently uses onediacritic, the acute accent, though traditionally a second was used, the overdot. If diacritics are unavailable, e.g. on a computer usingASCII, the overdot is replaced by a following⟨h⟩, e.g.Ḃí sé →Bhí sé "He/It was" and there is no standard for replacing an acute accent, though sometimes it is indicated by a followingslash, e.g.fírinne →fi/rinne "truth".^[14]

Theacute accent (⟨◌́⟩;agúid or(síneadh) fada "long (extension)")^a is used to indicate a long vowel, as inbád/bˠaːd̪ˠ/ "boat". However, there are other conventions to indicate a long vowel, such as:

• A following⟨rd, rl, rn, rr⟩, e.g.ard/aːɾˠd̪ˠ/ "high",eirleach/ˈeːɾˠlʲəx/ "destruction",dorn/d̪ˠoːɾˠn̪ˠ/ "fist", and, in Connacht, a word-final⟨m⟩, e.g.am/aːmˠ/ "time".
• The digraphs⟨ae, ao, eo⟩, e.g.aerach/ˈeːɾˠəx/ "gay",maol/mˠiːlˠ/ "bare",ceol/coːlˠ/ "music".
• The tri/tetragraphs⟨omh(a), umh(a)⟩, e.g.comharsa/ˈkoːɾˠsˠə/ "neighbour",Mumhain/mˠuːnʲ/ "Munster".
• ⟨i⟩ and⟨u⟩ before⟨á⟩ or⟨ó⟩, e.g.fiáin/ˈfʲiːaːnʲ/ "wild",ruóg/ˈɾˠuːoːɡ/ "twine".

Theoverdot (⟨◌̇⟩;ponc séimhithe "dot of lenition") was traditionally used to indicatelenition, thoughAn Caighdeán exclusively uses a following⟨h⟩ for this purpose. InOld Irish, the overdot was only used for⟨ḟ, ṡ⟩, while the following⟨h⟩ was used for⟨ch, ph, th⟩ and the lenition of other letters was not indicated. Later the two methods were used in parallel to represent lenition of any consonant (except⟨l, n, r⟩) until the standard practice became to use the overdot in Gaelic type and the following⟨h⟩ in Roman type. Thus the dotted letters (litreacha buailte "struck letters")⟨ḃ, ċ, ḋ, ḟ, ġ, ṁ, ṗ, ṡ, ṫ⟩ are equivalent to letters followed by a⟨h⟩, i.e.⟨bh, ch, dh, fh, gh, mh, ph, sh, th⟩.

Lowercase⟨i⟩ has notittle in Gaelic type. However, as printed and electronic material like books, newspapers and web pages use Roman type almost invariably, the tittle is generally shown. Irish does notgraphemically distinguishdotted i anddotless ı, i.e. they are not different letters as they are in, e.g.Turkish andAzeri.

Irishpunctuation is similar to English. An apparent exception is theTironian et (⟨⁊⟩;agus) which abbreviates the wordagus "and", like theampersand (⟨&⟩) abbreviates "and" in English. It is generally substituted by aseven (⟨7⟩) in texts.

Ahyphen (fleiscín) is used in Irish after⟨t, n⟩ when prefixed to a masculine vowel-initial word as aninitial mutation, e.g.an t-arán "the bread",a n-iníon "their daughter". However, it is omitted when the vowel is capitalised, e.g.an tAlbanach "the Scotsman",Ár nAthair "Our Father". No hyphen is used when⟨h⟩ is prefixed to a vowel-initial word, e.g.a hiníon "her daughter".

A hyphen is also used incompound words under certain circumstances:

• between two vowels, e.g.mí-ádh "misfortune"
• between two similar consonants, e.g.droch-chaint "bad language",grod-díol "prompt payment"
• in a three-part compound, e.g.buan-chomhchoiste "permanent joint committee"
• after the prefixesdo-,fo-,so- before a word beginning with⟨bha, bhla, bhra, dha, gha, ghla, ghra, mha⟩, e.g.do-bhlasta "bad tasting",fo-ghlac "subsume",so-mharfacht "mortality"
• in capitalised titles, e.g.An Príomh-Bhreitheamh "the Chief Justice"
• afteran- "very" anddea- "good", e.g.an-mhór "very big",dea-mhéin "goodwill"

Anapostrophe (uaschamóg) is used to indicate an omitted vowel in the following cases:

• the prepositionsde "from" anddo "to" both becomed' before a vowel or⟨fh⟩ + vowel, as inThit sí d'each "She fell from a horse" andTabhair d'fhear an tí é "Give it to the landlord"
• the possessive pronounsmo "my" anddo "your (singular)" becomem' andd' before a vowel or⟨fh⟩ + vowel, as inm'óige "my youth",d'fhiacail "your tooth"
• the preverbalparticledo becomesd' before a vowel or⟨fh⟩ + vowel, as ind'ardaigh mé "I raised",d'fhanfadh sé "he would wait"
• the copular particleba becomesb' before a vowel or⟨fh⟩ + vowel, as inB'ait liom é sin "I found that odd" andb'fhéidir "maybe". However,ba is used before the pronounsé,í,iad, as inBa iad na ginearáil a choinnigh an chumhacht "It was the generals who kept the power"

Capitalisation rules are similar to English. However, a prefixed letter remains in lowercase when the base initial is capitalised (an tSín "China"). For text written inall caps, the prefixed letter is kept in lowercase, orsmall caps (STAIR NAHÉIREANN "THE HISTORY OF IRELAND").^[15] An initial capital is used for:^[16]

• Start of sentences
• Names of people, places (except the wordsan,na,de),^[17] languages, and adjectives of people and places (Micheál Ó Murchú "Michael Murphy";Máire Mhac an tSaoi "Mary McEntee";de Búrca "Burke";Sliabh na mBan "Slievenamon";Fraincis "French";bia Iodálach "Italian food")
• Names of months, weeks and feast-days (Meán Fómhair "September";an Luan "Monday";Oíche Nollag "Christmas Eve")
• Dé "day" (Dé Luain "on Monday")
• Definitetitles^[18]

Most Irishabbreviations are straightforward, e.g.leathanach →lch. ("page → p.") andmar shampla →m.sh. ("exempli gratia (for example) → e.g."), but two that require explanation are:is é sin →.i. ("that is → i.e.") andagus araile →⁊rl./srl. ("et cetera (and so forth) → &c./etc.").^[19] Like⟨th⟩ in English,⟨ú⟩ follows anordinal numeral, e.g.Is é Lá Fheile Phádraig an 17ú lá den Márta "St. Patrick's day is the 17th [day] of March".

The literaryClassical Irish which survived till the 17th century was archaic; the first attempt at simplification was not until 1639.^[20] The spelling represented adialect continuum includingdistinctions lost in all surviving dialects by theGaelic revival of the late 19th century.

The idea of aspelling reform, linked to the use of Roman or Gaelic type, was controversial in the early decades of the 20th century.^[21] TheIrish Texts Society's 1904Irish-English dictionary byPatrick S. Dinneen used traditional spellings.^[21] After the creation of theIrish Free State in 1922, all Acts of theOireachtas were translated into Irish, initially using Dinneen's spellings, with a list of simplifications accumulating over the years.^[21] WhenÉamon de Valera becamePresident of the Executive Council after the1932 election, policy reverted to older spellings, which were used in the enrolled text of the1937 Constitution.^[21] In 1941, de Valera decided to publish a "popular edition" of the Constitution with simplified spelling and established a committee of experts, which failed to agree on recommendations.^[21][22] Instead, the Oireachtas' own translation service prepared a booklet,Litriú na Gaeilge: Lámhleabhar an Chaighdeáin Oifigiúil, published in 1945.^[22]

Some pre-reform spellings criticised byT. F. O'Rahilly and their modern forms include:^[21]beirbhiughadh →beiriú,imthighthe →imithe,faghbháil →fáil,urradhas →urrús,filidheacht →filíocht.

The booklet was expanded in 1947,^[23] and republished asAn Caighdeán Oifigiúil "The OfficialStandard" in 1958, combined with the standard grammar of 1953.^[24] It attracted initial criticism as unhistorical and artificial; some spellings fail to represent the pronunciation of some dialects, while others preserveletters unpronounced in any dialect.^[24] Its status was reinforced by use in thecivil service and as a guide forTomás de Bhaldraithe's 1959 English–Irish dictionary andNiall Ó Dónaill's 1977 Irish–English dictionary.^[24] A review of the written standard, including spelling, was announced in 2010, aiming to improve "simplicity, internal consistency, and logic".^[25] The result was the 2017 update ofAn Caighdeán Oifigiúil.^[26]

• Irish Braille
• Irish initial mutations
• Irish manual alphabet
• Scottish Gaelic orthography

• ^a Vowels with an acute accent are read as [á/é/í/ó/ú]fada "long [á/é/í/ó/ú]".
• ^b In the verbal adjective suffix, -⟨th⟩- becomes⟨t⟩ after⟨d, gh, l, n, s, t, th⟩ (⟨gh, th⟩ are deleted before it is added) and it becomes⟨f⟩ after⟨bh, mh⟩ which are deleted before it is added.
• ^c After consonants,/h/ is silent, but devoices preceding voiced consonants. SeeIrish phonology.

• Gramadach na Gaeilge agus Litriú na Gaeilge: An Caighdeán Oifigiúil. Dublin: Oifig an tSoláthair. 1994.
• Mac Eoin, Gearóid (1993). "Irish". In Martin J. Ball; James Fife (eds.).The Celtic Languages. London: Routledge. pp. 101–44.ISBN 0-415-01035-7.
• Ó Baoill, Dónall P. (1986).Lárchanúint don Ghaeilge (in Irish). Dublin: The Linguistics Institute of Ireland.ISBN 0-946452-06-7.
• Ó Murchú, Máirtín (1977)."Successes and Failures in the Modernization of Irish Spelling". In Fishman, Joshua A. (ed.).Advances in the Creation and Revision of Writing Systems. De Gruyter. pp. 267–289.ISBN 9783110807097.
• Ó Siadhail, Mícheál (1988).Learning Irish (2nd ed.). New Haven: Yale University Press.ISBN 0-300-04224-8.
• Stenson, Nancy; Hickey, Tina (2018).Understanding Irish Spelling A Handbook for Teachers and Learners(PDF). An Chomhairle um Oideachas Gaeltachta & Gaelscolaíochta.
• Graiméar Gaeilge na mBráithre Críostaí (in Irish). Dublin:An Gúm. 1999.ISBN 1-85791-327-2.

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