Irish orthography is the set of conventions used to write Irish. A spelling reform in the mid-20th century led to An Caighdeán Oifigiúil, the modern standard written form used by the Government of Ireland, which regulates both spelling and grammar.^[1] The reform removed inter-dialectal silent letters, simplified some letter 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 Irish dialects to a high degree despite their considerable phonological variation, e.g. crann ("tree") is read /kɾˠan̪ˠ/ in Mayo and Ulster, /kɾˠaːn̪ˠ/ in Galway, or /kɾˠəun̪ˠ/ in Munster. 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 the writing system used to write Irish since the 5th century, when it replaced Ogham, which was used to write Primitive Irish and Old Irish.^[4] Prior to the mid-20th century, Gaelic type (cló Gaelach) was the main typeface used to write Irish; now, it is usually replaced by Roman type (cló Rómhánach). The use of Ogham and Gaelic type today is restricted to decorative or self-consciously traditional contexts. The dot above a lenited letter in Gaelic type is usually replaced by a following ⟨h⟩ in Roman type (e.g. ⟨ċ⟩ → ⟨ch⟩).^[5]

Letters and letter names

The traditional Irish alphabet (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 modern loanwords/words of foreign origin. ⟨v⟩ occurs in a small number of (mainly onomatopoeic) native words (e.g. vácarnach "to quack" and vrác "caw") and colloquialisms (e.g. víog for bíog "chirp" and vís for bís "screw").^[6] ⟨h⟩, when not prefixed to a word initial vowel or after a consonant to show lenition, primarily occurs word initially in loanwords, e.g. hata "hat". ⟨k⟩ is the only letter not listed by Ó Dónaill.

Vowels may be accented with an acute accent (⟨á, é, í, ó, ú⟩; see below).^[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 original Latin names), similar to other languages that use a Latin script alphabet. Tree names were historically used to name the letters. Tradition taught that they all derived from the names of Ogham letters, though it is now known that only some of the earliest were named after trees.

More information Letter, Name ...

Letter	Name [8][3]	Name (IPA)	Tree Name (Bríatharogam)	Ogham equivalent	Notes
Aa	á a	/aː/	ailm (pine)	ᚐ
Bb	bé	/bʲeː/	beith (birch)	ᚁ
Cc	cé	/ceː/	coll (hazel)	ᚉ
Dd	dé	/dʲeː/	dair (oak)	ᚇ
Ee	é a	/eː/	eadhadh (poplar)	ᚓ
Ff	eif	/ɛfʲ/	fearn (alder)	ᚃ
Gg	gé	/ɟeː/	gort (ivy)	ᚌ
Hh	héis	/heːʃ/	uath (hawthorn)	ᚆ
Ii	í a	/iː/	iodhadh (yew)	ᚔ
Jj	jé	/dʒeː/			[dʒ] is a foreign sound.
Kk	cá	/kaː/
Ll	eil	/ɛlʲ/	luis (rowan)	ᚂ
Mm	eim	/ɛmʲ/	muin (vine)	ᚋ
Nn	ein	/ɛnʲ/	nion (ash)	ᚅ
Oo	ó a	/oː/	onn (gorse)	ᚑ
Pp	pé	/pʲeː/	ifín (gooseberry or thorn)	ᚘ	See forfeda.
			peith (dwarf alder)	ᚚ
Qq	cú	/kuː/		ᚊ	⟨Q⟩ is used to transliterate ceirt (apple).
Rr	ear	/aɾˠ/	ruis (elder)	ᚏ
Ss	eas	/asˠ/	sail (willow)	ᚄ
Tt	té	/tʲeː/	tinne (holly)	ᚈ
Uu	ú a	/uː/	úr (heather)	ᚒ
Vv	vé	/vʲeː/
Ww	wae	/weː/
Xx	eacs	/ɛksˠ/
Yy	yé	/jeː/
Zz	zae	/zˠeː/		ᚎ	⟨Z⟩ is used to transliterate straif (blackthorn); [zˠ] is a foreign sound.

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In grapheme to phoneme 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 the letter(s) are not pronounced.
• The IPA transcriptions of examples on this page are in Connacht Irish.

See Irish phonology for an explanation of the symbols used and Irish initial mutations for an explanation of eclipsis and lenition.

After a short vowel, an unwritten epenthetic /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 a morpheme 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 after long vowels and diphthongs, e.g. téarma /tʲeːɾˠmˠə/ "term" or dualgas /ˈd̪ˠuəlˠɡəsˠ/ "duty", or across morpheme boundaries (i.e. after prefixes and in compound words), e.g. garmhac /ˈɡaɾˠwak/ "grandson" (from gar- "close, near" + mac "son"), an-chiúin /ˈan̪ˠçuːnʲ/ "very quiet" (from an- "very" + ciúin "quiet"), carrbhealach /ˈkaːɾˠvʲalˠəx/ "carriageway, roadway" (from carr "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⟩.

In verb forms, some letters and letter combinations are pronounced differently from elsewhere.

An Caighdeán Oifigiúil currently uses one diacritic, the acute accent, though traditionally a second was used, the overdot. If diacritics are unavailable, e.g. on a computer using ASCII, 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 following slash, e.g. fírinne → fi/rinne "truth".^[12]

The acute accent (⟨◌́⟩; agúid or (síneadh) fada "long (sign)")^a is used to indicate a long vowel, as in bád /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".

The overdot (⟨◌̇⟩; ponc séimhithe "dot of lenition") was traditionally used to indicate lenition, though An Caighdeán exclusively uses a following ⟨h⟩ for this purpose. In Old 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 no tittle in Gaelic type, and road signs in the Republic of Ireland. However, as printed and electronic material like books, newspapers and web pages use Roman type almost invariably, the tittle is generally shown. Irish does not graphemically distinguish dotted i and dotless ı, i.e. they are not different letters as they are in, e.g. Turkish and Azeri.

Irish punctuation is similar to English. An apparent exception is the Tironian et (⟨⁊⟩; agus) which abbreviates the word agus "and", like the ampersand (⟨&⟩) abbreviates "and" in English. It is generally substituted by a seven (⟨7⟩) in texts.

A hyphen (fleiscín) is used in Irish after ⟨t, n⟩ when prefixed to a masculine vowel-initial word as an initial 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 in compound 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 prefixes do-, 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"
• after an- "very" and dea- "good", e.g. an-mhór "very big", dea-mhéin "goodwill"

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

• the prepositions de "from" and do "to" both become d' before a vowel or ⟨fh⟩ + vowel, as in Thit sí d'each "She fell from a horse" and Tabhair d'fhear an tí é "Give it to the landlord"
• the possessive pronouns mo "my" and do "your (singular)" become m' and d' before a vowel or ⟨fh⟩ + vowel, as in m'óige "my youth", d'fhiacail "your tooth"
• the preverbal particle do becomes d' before a vowel or ⟨fh⟩ + vowel, as in d'ardaigh mé "I raised", d'fhanfadh sé "he would wait"
• the copular particle ba becomes b' before a vowel or ⟨fh⟩ + vowel, as in B'ait liom é sin "I found that odd" and b'fhéidir "maybe". However, ba is used before the pronouns é, í, iad, as in Ba 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 in all caps, the prefixed letter is kept in lowercase, or small caps (STAIR NA HÉIREANN "THE HISTORY OF IRELAND").^[13] An initial capital is used for:^[14]

• Start of sentences
• Names of people, places (except the words an, na, de),^[15] 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")
• Definite titles^[16]

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

The literary Classical Irish which survived till the 17th century was archaic; the first attempt at simplification was not until 1639.^[18] The spelling represented a dialect continuum including distinctions lost in all surviving dialects by the Gaelic revival of the late 19th century.

The idea of a spelling reform, linked to the use of Roman or Gaelic type, was controversial in the early decades of the 20th century.^[19] The Irish Texts Society's 1904 Irish-English dictionary by Patrick S. Dinneen used traditional spellings.^[19] After the creation of the Irish Free State in 1922, all Acts of the Oireachtas were translated into Irish, initially using Dinneen's spellings, with a list of simplifications accumulating over the years.^[19] When Éamon de Valera became President of the Executive Council after the 1932 election, policy reverted to older spellings, which were used in the enrolled text of the 1937 Constitution.^[19] 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.^[19][20] Instead, the Oireachtas' own translation service prepared a booklet, Litriú na Gaeilge: Lámhleabhar an Chaighdeáin Oifigiúil, published in 1945.^[20]

Some pre-reform spellings criticised by T. F. O'Rahilly and their modern forms include:^[19] beirbhiughadh → beiriú, imthighthe → imithe, faghbháil → fáil, urradhas → urrús, filidheacht → filíocht.

The booklet was expanded in 1947,^[21] and republished as An Caighdeán Oifigiúil "The Official Standard" in 1958, combined with the standard grammar of 1953.^[22] It attracted initial criticism as unhistorical and artificial; some spellings fail to represent the pronunciation of some dialects, while others preserve letters unpronounced in any dialect.^[22] Its status was reinforced by use in the civil service and as a guide for Tomás de Bhaldraithe's 1959 English–Irish dictionary and Niall Ó Dónaill's 1977 Irish–English dictionary.^[22] A review of the written standard, including spelling, was announced in 2010, aiming to improve "simplicity, internal consistency, and logic".^[23] The result was the 2017 update of An Caighdeán Oifigiúil.^[24]

• Irish Braille
• 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. See Irish phonology.