Appendix:Irish mutations

Irish, like all modern Celtic languages, is characterized by its initial consonant mutations. These mutations affect the initial consonant of a word depending on morphological and syntactic conditions. The mutations are an important tool in understanding the relationship between two words and can differentiate meaning.

Irish uses two mutations on consonants: lenition and eclipsis. There are also three mutations—eclipsis, t-prothesis, and h-prothesis—found on vowel-initial words.

The unmutated form (the "base" form) is known as the radical.

Words subject to mutation
Not all words are subject to mutation. The only types of words subject to mutation are:
 * Nouns
 * Verbs
 * Adjectives (rarely subject to eclipsis outside fixed expressions)
 * Third-person disjunctive pronouns (é, í, ea, and iad)

All other words (adverbs, determiners, prepositions, etc.) are not subject to mutation.

Words that trigger mutation always come immediately before the words they modify, and apart from nouns, almost all such words have to be repeated for each word (thus but ). There are several exceptions, however, such as and, thus  ,.

Effects of lenition
Consonants change as follows when they undergo lenition:

Note: sc, sf, sm, sp, and st do not mutate and other consonants do not change under lenition.

After proclitics
After the definite article and contractions of it with prepositions, e.g., :

The definite article triggers lenition of:
 * 1) a feminine noun in the nominative singular
 * 2) a masculine noun in the genitive singular
 * 3) a noun in the dative singular, when the article follows one of the contractions,  or  ( before a vowel sound) (note: in some dialects, lenition occurs also after other preposition + article combinations):
 * d and t are never lenited after the article:
 * , although is feminine nominative singular
 * , although follows
 * d and t are never lenited after the article:
 * , although is feminine nominative singular
 * , although follows
 * , although is feminine nominative singular
 * , although follows


 * Where s would be lenited after the article, it becomes ts (rather than sh ):
 * (fem. nom. sg.)
 * (fem. dat. sg.)
 * (masc. gen. sg.)


 * In some dialects, this same change happens after any n and l in a leniting environment:
 * (standard )
 * (standard )

After the vocative particle 

After possessive determiners

The possessive determiners that trigger lenition are, ,

After certain prepositions

After the preterite/conditional of the copula, except in Northern Irish when the word starts with t, d and optionally s:
 * , Northern Irish
 * , Northern Irish

After preterite preverbal particles

After certain preverbal particles

A verb in the preterite, imperfect or conditional

These were originally preceded by the particle and often still are in Munster.

In modifier + head constructions
Lenition is blocked in these constructions if two coronals other than r (i.e. d, l, n, s, t) are adjacent.

After certain numbers

When the singular form is used after numbers, it is lenited in the following cases. Always with aon "one" and dhá "two" (dá with the article: an dá); note that d(h)á is followed by the dual. The other numbers, 3 to 6, do not cause lenition when followed by the plural.


 * "one cow"
 * , alt.  (dual) "two houses"
 * , alt.  (plural) "three boats"
 * , alt.  (plural) "four dogs"
 * , alt. (plural) "five pounds"
 * , alt. (plural) "six months"

Note that there is a subtle semantic difference between the use of the singular and plural, that of group unit, e.g. trí chearc "three chickens (as one lot)", or not as a unit, e.g. trí cearca "three chickens not as part of a single group".

After preposed adjectives

Constructions of adjective + noun are written as compounds.
 * "old woman"
 * "bad person"
 * "good health"
 * "modern language"
 * "stormy sea"
 * "true skin"
 * "high pressure"
 * "young man"

After most prefixes
 * "very small"
 * "too small"
 * "retake"
 * "new year"
 * "undeniable"
 * "saucer"
 * "overalls"
 * "interconfessional"
 * "polygamy"
 * "stepmother"
 * "unhappy"
 * "insomnia"
 * "capital city"
 * "fragile"

The second part of a compound
 * "noun" (lit. "name word")
 * "dark blue, navy blue" (lit. "black-blue")
 * "national debt"

In head + modifier constructions
In these constructions coronals are lenited even following other coronals.

Genitive nouns in certain circumstances
 * "rainy weather" (lenition after a feminine singular noun)
 * "bottles of juice" (lenition after a plural ending in a slender consonant)
 * "Seán's house" (lenition of a definite noun in the genitive)

Postposed adjectives in certain circumstances
 * "a pretty woman" (lenition after a feminine singular noun)
 * na  "the big men" (lenition after a plural noun ending in a slender consonant)
 * ainm an  "the name of the small man" (lenition after a masculine singular noun in the genitive)
 * sa  "in the big tree" (lenition after a noun lenited by virtue of being in the dative after den, don, or sa(n))

Effects of eclipsis
1. Consonants change as follows when they undergo eclipsis. When eclipsed words are capitalized, it is the consonant of the radical that is capitalized, while the letter(s) showing eclipses remain small.

The other consonants do not change under eclipsis.

2. A vowel receives a preceding n- (pronounced before a, o, u,  before e, i). The hyphen is not used before a capital letter.

After plural possessive determiners
The possessive determiners that trigger eclipsis are, ,
 * ár "our friends"
 * bhur "your (pl.) children"
 * a "their boat"

After certain numbers
The numbers that trigger eclipsis (the noun being in the singular) are:
 * "seven horses"
 * "eight donkeys"
 * "nine cats"
 * "ten pens"

After the preposition
Before a vowel is written instead of i n-, though before the spelling reforms of the mid-20th century this was not the case.
 * i "in a house"
 * in "in Ireland"
 * i

Genitive plural nouns after the definite article
The genitive plural article eclipses a following noun:
 * na "of the donkeys"
 * na "of the words"

Dative singular nouns after the definite article
In western dialects, nouns beginning with a noncoronal consonant are eclipsed after combinations of preposition + article in the singular (except, , and sa(n), which trigger lenition). In southern dialects, t and d are also affected, and optionally s: A vowel-initial word is not affected after the definite article an.
 * an "by the man"
 * an "on the tree"
 * an (Connacht), ar an  (West) "on the door"

After certain preverbal particles
A vowel-initial word is not affected after the interrogative particle an.
 * an poll  na coiníní as "the hole that the rabbits come out of"
 * sé gach lá? "Does he come every day?"
 * mo spéaclaí? "Where are my glasses?"
 * Dúirt sé  sé. "He said that he would come."
 * a fhios sin agam "if I had known that"

Changes to vowel-initial words
Vowel-initial words undergo eclipsis, as explained above, except after an.

A vowel-initial word does not change where lenition is expected:
 * an "the night" (feminine singular nominative noun after definite article)
 * an "of the water" (masculine singular genitive noun after definite article)
 * ó "from Scotland" (noun after leniting preposition)
 * "grandfather" (noun after preposed adjective: "old" +  "father")

But where neither eclipsis nor lenition is expected, an initial vowel may acquire a prothetic t- or h- onset consonant.

T-prothesis
A vowel-initial masculine singular nominative noun takes the prothetic onset t- after the definite article. The hyphen is not used before a capital letter: T-prothesis is also found with vowel-initial numerals (attributive or ordinal) after the article in the nominative singular with both masculine and feminine nouns:
 * an "the water" (masculine singular nominative)
 * an "the Irishman" (masculine singular nominative)
 * an bhád ("the one boat")
 * an t-ochtú bó ("the eighth cow")
 * an t-aonú lá fichead (“the twenty-first day”)

H-prothesis
The prothetic onset h- comes only when both the following conditions are met:
 * 1) a proclitic causes neither lenition nor eclipsis of consonants
 * 2) a proclitic itself ends in a vowel sound

There is no need for adding a hyphen before a lowercase letter as with t-prothesis as h does not occur initially in native Irish words outside prothesis.

Examples of h-prothesis
 * (after possessive pronoun )
 * (after preposition )
 * (after preposition )
 * (on feminine singular genitive noun after definite article )
 * (on plural nominative/dative noun after definite article )
 * (after )
 * (after adverbial particle )
 * (after negative imperative particle )
 * (after an ordinal numeral)

Colloquially in some dialects, verbs beginning with a vowel undergo h-prothesis in the past indicative autonomous form; there is no triggering proclitic in this case: