Caibidil a Ceathair Déag: 

Initial Mutations (na hAthruithe Tosaigh)

t-, n-, h-, d'-prefixes (na Réamhlitreacha)

Not only lenition (séimhiú) and eclipsis (urú), but also (in part also in cooperation) the prefixing of the letters t, h, n, d' change the beginnings of words.

Here is a bit about the cause of these prefixes (except th d'-prefix which is explained below)


t-prefix (an réamhlitir t)

preceding s: ts  capitalised: tS
preceding a vowel: t-a, t-e, etc. capitalised: tA, tE, etc. e.g. an tÉireannach = the Irishman

The s after t-prefix is not spoken: an tsráid [tra:d']


  1. preceding nouns with a vowel after the article an
  2. preceding nouns with s- after the article an (instead of lenition of the s; occurs only if it's followed by a vowel or l, n, r)
  3. preceding numbers with a vowel after the article an in the nominative/accusative no matter if it's followed by a feminine or masculine noun:  an t-aon bhád amháin = the one boat, an t-aonú .....deag, an t-ochtú, an t-ochtódú, an t-ochtar, an t-ocht. (not in the dative: ar an ochtar)
  4. preceding s- after -n, if -n occurs in another word than the article (e.g. colloq. in Árainn an-tsean = very old instead of the standard an-sean), often after aon (colloq. aon tsúil = an eye ; probably etymolog. wrong, in analogy to the t-prefix after the article, standard: aon súil)
    Sometimes this occurs in names, e.g. after Clann = Family : Clann tSuibhne = MacSweeney Family

h-prefix (an réamhlitir h)

preceding a vowel: ha, he, etc. capitalised:  hA, hE, etc. e.g.: Poblacht na hÉireann = Republic of Ireland


h-prefix is only used preceding words beginning in a vowel. It generally serves to simplify pronunciation, if 2 vowels clash and neither lenition nor eclipsis are necessary.

  1. preceding nouns
  2. preceding pronouns (é, í, iad, ea, eo, in, iúd)
  3. preceding adjectives / adverbs
  4. preceding verbs
  5. preceding numeral words 1 and 8 after the numeral particle a: a haon , a hocht
  6. in adverbial days of the week with ( = day) Dé hAoine = Friday

n-prefix (an réamhlitir n)

preceding a vowel: n-a, n-e, etc. by capitalisation:  nA, nE:   e.g.: Tir na nÓg = Land of Youth


  1. preceding a vowel by expressions/particles actually requiring eclipsis : ár n-uncail = our uncle;  (unless it already ends in -n, also not after an: ar an úll = on the apple !), not after the preposition i: but instead in: in Éirinn = in Ireland (this is purely a written convention, the pronunciation is the same as i nÉireann, which also occasionally occurs.
  2. after le in the meaning "(in order) to " (in Connacht):   cad a bheidh agat le n-ól = what will you drink? ("what will you have to drink?"), althought after le normally no eclipsis occurs.

d'-prefix (an réamhlitir d')

This is actually not a "prefix" in the sense of the other prefixes, because d' is only a short form of the independent particle do. In this way it's quite different from the other prefixes.
Do is a past verbal particle to denote the preterite, imperfect and conditional tenses. It's only still in use anymore in Munster preceding consonants: (do dhéineas = ich machte). Preceding a vowel in the form d' in all dialects and in the standard.
The abbreviation of do explains also the apostrophe by d'.

preceding a vowel and preceding fh: d'a, d'e, d'fh, capitalised: D'a, D'e, D'fh etc.


  1. preceding a vowel and fh by verbs in the preterite, imperfect, conditional. d'ól mé = I drank , d'ólinn = I used to drink, d'ólfinn = I would drink, d'fhoghlain the sé = he learned

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© Lars Braesicke 1999 / 2000

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