Irish orthography

 ( Orthography ) 

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

• Unstressed short vowels are generally reduced to .
• is silent before a broad vowel.
• is silent before and after a vowel (except sometimes in ).
• have multiple pronunciations that depend on adjacent consonants.
• Diacritic vowels () represent Vowel length and in digraphs and trigraphs 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 "sixth", ríúil "royal, kingly, majestic", báíocht "sympathy", etc.
• and are long before , e.g. fiáin "wild", ruóg "twine"
• A following lengthens some vowels and in Munster and Connacht a following syllable-final or word-final may lengthen or diphthongise some vowels depending on dialect.

Epenthesis does not occur after Vowel length and diphthongs, e.g. téarma "term" or dualgas "duty", or across morpheme boundaries (i.e. after prefixes and in compound words), e.g. garmhac "grandson" (from gar- "close, near" + mac "son"), an-chiúin "very quiet" (from an- "very" + ciúin "quiet"), carrbhealach "carriageway, roadway" (from carr "car" + bealach "way, road").

In Munster, epenthesis also occurs across morpheme boundaries, when follow (after any vowel) or (after short vowels), and when follows .

The acute accent (; agúid or (síneadh) fada "long (sign)") is used to indicate a long vowel, as in bád "boat". However, there are other conventions to indicate a long vowel, such as:

• A following , e.g. ard "high", eirleach "destruction", dorn "fist", and, in Connacht, a word-final , e.g. am "time".
• The digraphs , e.g. aerach "gay", maol "bare", ceol "music".
• The tri/tetragraphs , e.g. comharsa "neighbour", Mumhain "Munster".
• and before or , e.g. fiáin "wild", ruóg "twine".

The overdot (; ponc séimhithe "dot of lenition") was traditionally used to indicate lenition, though An Caighdeán exclusively uses a following for this purpose. In Old Irish, the overdot was only used for , while the following was used for and the lenition of other letters was not indicated. Later the two methods were used in parallel to represent lenition of any consonant (except ) until the standard practice became to use the overdot in Gaelic type and the following in Roman type. Thus the dotted letters (litreacha buailte "struck letters") are equivalent to letters followed by a , i.e. .

Letter case 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 Grapheme distinguish dotted i and Dotless I, i.e. they are not different letters as they are in, e.g. Turkish language and Azeri.

A hyphen (fleiscín) is used in Irish after 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 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 , 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 + 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 + vowel, as in m'óige "my youth", d'fhiacail "your tooth"
• the preverbal particle do becomes d' before a vowel or + vowel, as in d'ardaigh mé "I raised", d'fhanfadh sé "he would wait"
• the copular particle ba becomes b' before a vowel or + 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"

• Start of sentences
• Names of people, places (except the words an, na, de),Graiméar Gaeilge na mBráithre Críostaí, §§ 3.1, 7.6, 10.2-10.3 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 Graiméar Gaeilge na mBráithre Críostaí, §§ 3.1, 3.4

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.