Prefixes (t-, h-, n-)

An explanation of the t-, h-, and n- prefixes in Irish, which alter the beginning of words, similar to lenition and eclipsis.

Prefix Mutation Grammar Article

In addition to lenition and eclipsis, Irish uses three prefixes—t-, h-, and n-—to change the initial sound of a word. These changes, known as réamhlitreacha (prefix letters), are often triggered by preceding particles, especially the definite article.

The t-Prefix

The t-prefix is added to words beginning with a vowel or the letter s. Its application depends on two different principles, but in the standard language, it almost always appears after the singular article an.

Spelling and Pronunciation

  • Before a vowel, it is written with a hyphen: t-a, t-e. In capital letters, the hyphen is omitted: tA, tE.
    • an t-Éireannach - the Irishman
  • Before s, it is written as ts. In capital letters, only the s is capitalised: tS.
    • an tsráid - the street

Usage with Vowels

The t-prefix is used before masculine singular nouns that begin with a vowel, but only in the nominative and accusative cases after the article an.

  • an t-úll - the apple

It is not used in the genitive or dative cases.

  • craiceann an úill - the skin of the apple (genitive)
  • ar an úll - on the apple (dative)

Usage with s-

The t-prefix is used before nouns beginning with s- (followed by a vowel, l, n, or r) in specific situations after the article an. This usage effectively replaces lenition, which cannot apply to s.

Nominative and Accusative (Feminine Nouns) Feminine nouns in the nominative/accusative singular take a t-prefix.

  • an tsráid - the street

Genitive (Masculine Nouns) Masculine nouns in the genitive singular take a t-prefix.

  • an tsagairt - of the priest

Dative (After Prepositions) Usage in the dative case (after a preposition + an) varies by dialect.

Usage with Numbers

The t-prefix appears before numbers beginning with a vowel after the article an in the nominative/accusative.

  • an t-aon bhád amháin - the one boat
  • an t-ochtú - the eighth
  • an t-ochtar - the eight people

However, it is not used in the dative: ar an ochtar (on the eight people).

Dialectal and Historical Usage

In some dialects, a t-prefix appears before s- in other contexts, particularly after words ending in -n or -l.

  • an-tsean - very old (Standard: an-sean)
  • aon tsúil - one eye (Standard: aon súil)

This is also seen in some proper names and place names.

  • Clann tSuibhne - the MacSweeney family
  • Cionn tSáile - Kinsale
Historical note

This dialectal usage is generally considered etymologically incorrect, as the t- historically derives from the definite article. However, it is widespread and may be explained as a phonologically conditioned insertion. In some proper names like Clann tSuibhne, the t- may reflect an older form of the preceding word, such as *cland Shuibhne.

The h-Prefix

The h-prefix is only used before words that begin with a vowel. It serves to separate two adjacent vowel sounds where neither lenition nor eclipsis is required.

Spelling

The h is placed directly before the vowel: ha, he. In capital letters, only the original vowel is capitalised: hA, hE.

  • Poblacht na hÉireann - Republic of Ireland

Usage with Nouns

  • After the article na:
    • In the plural (nominative, accusative, dative): na héin - the birds
    • In the genitive singular of feminine nouns: na hoifige - of the office
  • After a (her):
    • a huncail - her uncle
    • a dhá húll - her two apples
  • After certain numbers:
    • After trí, ceithre, cúig, sé with plural nouns like uaire (hours) or orlaí (inches): trí huaire - three hours; cúig horlaí - five inches.
    • This does not apply to singular nouns: trí úll - three apples.
  • After ordinal numbers (except an chéad):
    • an tríú húll - the third apple
  • After non-leniting prepositions:
    • le hÚna - with Úna
    • go hÉirinn - to Ireland
  • After cá (which):
    • cá háit? - where? (literally “which place?”)
    • cá haois? - how old? (literally “which age?”)
  • In names with Ó:
    • Ó hEidhin, Ó hAnluain. The h disappears after leniting particles like Ní or Uí (Ní Eidhin).
  • After ní (negative copula) in specific cases:
    • With nouns like áibhéil (exaggeration), ionadh (wonder), ualach (burden): Ní hiontas ar bith é sin. - That is no wonder at all.
    • In set copular phrases: Ní heol dó a athrach. - He knows nothing else.
    • In some proverbs: Ní heolas go haontíos. - You don’t know someone until you live with them.

Usage with Pronouns

The h-prefix is used before the pronouns é, í, iad, ea, etc., in these contexts:

  • After ní (negative copula): ní hé - it is not he; ní hea - it is not so.
  • After cé (who): cé hé? - who is he?
  • After pé (whoever): pé hé tú féin - whoever you are.

Usage with Adjectives and Adverbs

  • After the adverbial particle go: go holc - badly.
  • After chomh (so, as): chomh holc - so bad.
  • After ní (negative copula) with specific adjectives like ionann (same) or ansa (difficult): ní hionann iad - they are not the same.
  • In set copular phrases: Ní heagal duit an madra. - You don’t need to be afraid of the dog.

Usage with Verbs

  • After the negative imperative particle ná: Ná habair é! - Don’t say it!
  • Before the autonomous form (Saorbhriathar) in certain non-standard or dialectal contexts, often reflecting the historical particle do:
    • Hóladh é. - It was drunk.
    • Níor hóladh é. - It was not drunk.

Other Cases

  • Before the numbers aon (1) and ocht (8) after the counting particle a: a haon, a hocht.
  • In the names of weekdays with Dé: Dé hAoine - Friday.

The n-Prefix

The n-prefix is the form that eclipsis takes before a vowel.

Spelling

The n- is attached with a hyphen. In capital letters, the hyphen is omitted: n-a, nA.

  • Tír na nÓg - The Land of Youth (literally “land of the youths”)

Usage

The n-prefix appears wherever a word or particle would cause eclipsis on a following word that begins with a vowel.

  • ár n-uncail - our uncle
  • i gcaitheamh na n-aoiseanna - throughout the ages

Other Prefixes (Contractions)

The following forms look like prefixes but are actually contractions of common words. They are always written with an apostrophe to show that letters have been omitted.

d’ (Past Particle)

This is a shortening of the past tense particle do. In most dialects, it only appears before verbs starting with a vowel or fh-.

  • d’ól mé - I drank

d’ / t’ (Possessive Pronoun)

These are contractions of the possessive pronoun do (your). d' is standard and common in Ulster, while t' is more common in other dialects.

  • d’athair / t’athair - your father

M’ (Possessive Pronoun)

This is a contraction of the possessive pronoun mo (my).

  • m’athair - my father

D’ (Preposition)

This can be a contraction of the prepositions do (to) or de (from, of).

  • d’athair - to a father / from a father

B’ / mb’ (Copula)

This is a contraction of ba, the past/conditional form of the copula. It becomes mb' after a particle that causes eclipsis.

  • b’fhéidir - perhaps (literally “it would be possible”)
  • gach rud dá mb’fhéidir - everything that would be possible