Irish/Reference/Grammatical Changes

Grammatical ChangesEdit

Irish is an inflected language. Words undergo pronunciation and spelling changes depending on the role they play in a sentence. Some of the most common changes are described below. Later in this Wikibook you will learn when to apply these changes.


Lenition is a "softening" (a.k.a. "aspiration") of the consonant sound at the beginning of a word or syllable. It only happens to certain sounds: b, c, d, f, g, m, p, s, t; other letters are unaffected. There are two ways lenition is shown in writing: the old style (seanchló), in which a dot is placed over the consonant, and the new/modern style, where an h is added after the consonant. Some of the many cases in which you use lenition are:

  • on feminine nominative singular nouns after the article (ex. an fhírinne = the truth)
  • on masculine genitive singular nouns after the article (ex. an chroí = of the heart)
  • on adjectives after a feminine nominative singular noun (ex. fírinne gheal = bright truth)
  • on adjectives after a masculine genitive singular noun (ex. an chroí dhubh = of the black heart)
  • on adjectives after weak plural nouns which end in a slender consonant (ex. fir bheaga = small men but croíthe beaga = small hearts)
  • after mo or do (ex. mo shaol = my life)
  • after a when it means "his" (ex. a shaol = his life)
  • after the vocative particle a (ex. A Dhia! = God!)
  • in the second part of a compound word (ex. seanmháthair = grandmother, literally "old mother")


One of the trickier exceptions to the normal lenition rules is the infamous "dentals-dots rule": if you have a d, t, or s (the consonants in "dots") which would be lenited, but the letter before it is one of d, n, t, l, or s (the consonants in "dentals"), you don't lenite it after all. Example: an domhain = of the world - you'd probably think to write an dhomhain since a masculine genitive noun after the article is normally lenited, but the dentals-dots rule overrides that. It's worth noting, however, that this rule does not apply to lenition of attributive adjectives. For example grian the = hot sun.

Other exceptionsEdit

In a similar vein to the dentals-dots rule, the letters b and p are left unlenited following an m, as in um bosca. This is a much more obscure exception than dentals-dots, so you won't run into it very often.

Also, the letter s is not lenited when it is directly followed by one of c, p, t, m, or f, since there's no way (in Irish) that you could pronounce something like shf or shc. There are no counterexceptions to this exception, at least. For example, you write do stair = "your history" instead of "do shtair".


Eclipsis is an "eclipsing" (obviously) of the initial consonant sound of a word by another consonant sound. It only affects seven sounds: b, c, d, f, g, p, and t; essentially what happens is that you only pronounce the eclipsing consonant(s) - the eclipsed letter gets totally left out of the pronunciation (except for ng). However, when writing one of these things you write the eclipsing letter followed by the eclipsed letter. The rules for what happens to each go like this:

  • b is eclipsed by m to become mb
  • c is eclipsed by g to become gc
  • d is eclipsed by n to become nd
  • f is eclipsed by bh to become bhf (two letters, but one sound)
  • g is eclipsed by n to become ng (note that this is pronounced not just as a straight n, but as the hybrid ng sound, much like an ng in English, or a 'ny' sound as in piñata)
  • p is eclipsed by b to become bp
  • t is eclipsed by d to become dt

These rules have to be memorized, but it really doesn't take long once you start using them.

Eclipsis is used in many cases (though not as many as lenition, by far), among which are these:

  • on plural genitive nouns after the article (ex. na bpóg = of the kisses)
  • after any of the plural possessive pronouns, like "our", "your" (pl.), "their" (ex. ár ngrá = our love, bhur bpósadh = your wedding, a gcostas = their cost)
  • after some preposition+article combinations - you'll have to memorize which ones, but they can be learned with use (ex. ar an mbord = on the table, ón gcósta = from the coast, as an bPoblacht = out of the Republic)
  • after the preposition i (ex. i mbosca = in a box)

Note the funky capitalization in eclipsed expressions: if you're capitalizing an eclipsed word, you put the eclipsed letter in uppercase, not the eclipsing letter (ex. as an bPoblacht from above, and also na bhFear = of the men). However if writing in all caps, you can put the eclipsing letter in uppercase - or you can leave it in lowercase. Both variants exist (ex. NA BHFEAR or NA bhFEAR).


Palatalisation (caolú), sometimes called "slenderizing", is a change made to the last group of vowels in a word which transforms the word from having a broad ending to a slender ending. Depalatalisation (leathnú) is the reverse change; it transforms a word from having a slender ending to a broad ending. These changes are used a lot in Irish, mostly for changing nouns between singular and plural, or for switching between the various cases (nominative, genitive, dative, vocative). Here are a few representative examples which show the kinds of vowel changes involved:

Caolú Leathnú
  • bád → báid
  • fear → fir
  • éan → éin
  • iasc → éisc
  • fionn → finn
  • síol → síl
  • máthair → máthar
  • greim → greama
  • mil → meala
  • bácéir → bácéara
  • cuid → coda
  • feadaíl → feadaíola

The usual rule for palatalisation is to add an i after the last vowel, and the usual rule for depalatalisation is to remove a trailing i. These usual cases are shown in the top row of the above table.

Initial hEdit

In some cases, when a word ending in a vowel (such as the preposition "le" or the plural definite article "na") is followed by a word beginning with a vowel, an initial "h" is added to the second word to make pronunciation easier.


Tá an bhialann in aice le hóstán.

Initial tsEdit

Under certain circumstances, feminine nouns beginning with "s" may be modified to "ts".

Contractions and compoundsEdit

Some Irish words are abbreviated, contracted, or compounded in specific ways. This is especially common when combining a preposition with a pronoun or article.

Contracting mo and doEdit

The possessive pronouns mo (my) and do (your [sing.]) are commonly contracted before an initial vowel"

mo dhearthaír do dhearthaír
m'uncail d'uncail

Prepositional PronounsEdit

When a preposition's object is a pronoun, Irish normally combines the two into a single prepositional pronoun.

Prepositions and ArticlesEdit

In some cases, when a preposition's object starts with something other than a pronoun, especially a direct article (an or na), the preposition will form a compound similar to a prepositional pronoun.


  • faoi + an = faoin
  • faoi + a [numerical particle] = faoina