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.
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:
- 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 do bhuachaillí agus do chaillíní (“to boys and girls”) but cait mhóra dhubha (“big black cats”)). There are several exceptions, however, such as idir...agus... (“between/both...and...”) and mar (“like, as”), thus idir fhir agus mhná (“both/between men and women”), mar dharacha agus mhailpeanna (“like oaks and maples”).
Effects of lenition
Consonants change as follows when they undergo lenition:
|b /bˠ/, /bʲ/||bh /w/~/vˠ/, /vʲ/|
|c /k/, /c/||ch /x/, /ç/|
|d /d̪ˠ/, /dʲ/||dh /ɣ/, /j/|
|f /fˠ/, /fʲ/||fh (silent)|
|g /ɡ/, /ɟ/||gh /ɣ/, /j/|
|m /mˠ/, /mʲ/||mh /w/~/vˠ/, /vʲ/|
|p /pˠ/, /pʲ/||ph /fˠ/, /fʲ/|
|s /sˠ/, /ʃ/||sh /h/|
|Note: sc, sf, sm, sp, and st do not mutate|
|t /t̪ˠ/, /tʲ/||th /h/|
Other consonants do not change under lenition.
Environments of lenition
The definite article triggers lenition of:
- a feminine noun in the nominative singular
- an bhean (“the woman”)
- a masculine noun in the genitive singular
- an fhir (“of the man”)
- a noun in the dative singular, when the article follows one of the contractions den (“from the”), don (“to the”) or sa (“in the”) (san 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:
- Where s would be lenited after the article, it becomes ts /t̪ˠ, tʲ/ (rather than sh /h/):
- In some dialects, this same change happens after any n and l in a leniting environment:
- After the vocative particle a
- After possessive determiners
- After certain prepositions
- de chrann (“out of a tree”)
- faoi chrann (“under a tree”)
- mar dhuine (“as a person”)
- ó Chorcaigh (“from Cork”)
- roimh mhaidin (“before morning”)
- trí shioc agus shneachta (“through frost and snow”)
- um Cháisc (“at Easter”)
- idir fhir agus mhná (“between men and women, both men and women”)
- ar bhord (“on a table”)
- After the preterite/conditional of the copula is, except in Northern Irish when the word starts with t, d and optionally s
- Ba dhuine mór é. (“He was a big person.”)
- Ba dheas uait é. (“That was nice of you.”), Northern Irish Ba deas uait é.
- After preterite preverbal particles
- Níor mhúinteoir é. (“He was not a teacher.”)
- Níor thug mé (“I didn’t give”)
- Ar shagart é? (“Was he a priest?”)
- Ar tháinig sé? (“Did he come?”)
- After certain preverbal particles
- ní thuigim (“I don’t understand”)
- má thagann sé (“if he comes”)
- an fear a thabharfaidh dom é (“the man who will give it to me”)
- A verb in the preterite, imperfect or conditional
These were originally preceded by the particle do and often still are in Munster.
- bhris mé (“I broke”)
- bhrisinn (“I used to break”)
- bhrisfinn (“I would break”)
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.
- aon bhó amháin "one cow"
- dhá theach, alt. dhá thigh (dual) "two houses"
- trí bhád, alt. trí báid (plural) "three boats"
- ceithre mhadra, alt. cheithre madraí (plural) "four dogs"
- cúig phunt, alt. puint (plural) "five pounds"
- sé mhí, alt. míonna (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.
- seanbhean "old woman"
- drochdhuine "bad person"
- dea-shláinte "good health"
- nuatheanga "modern language"
- tréanmhuir "stormy sea"
- fíorchneas "true skin"
- ardbhrú "high pressure"
- ógfhear "young man"
- After most prefixes
- an-bheag "very small"
- ró-bheag "too small"
- aisghabháil "retake"
- athbhliain "new year"
- dobhréagnaithe "undeniable"
- fochupán "saucer"
- forbhríste "overalls"
- idirchreidmheach "interconfessional"
- ilphósadh "polygamy"
- leasmháthair "stepmother"
- míshásta "unhappy"
- neamhchodladh "insomnia"
- príomhchathair "capital city"
- sobhriste "fragile"
- The second part of a compound
- ainmfhocal "noun" (lit. "name word")
- dúghorm "dark blue, navy blue" (lit. "black-blue")
- státfhiach "national debt"
In head + modifier constructions
In these constructions coronals are lenited even following other coronals.
- Genitive nouns in certain circumstances
- aimsir bháistí "rainy weather" (lenition after a feminine singular noun)
- buidéil shú "bottles of juice" (lenition after a plural ending in a slender consonant)
- teach Sheáin "Seán's house" (lenition of a definite noun in the genitive)
- Postposed adjectives in certain circumstances
- bean dheas "a pretty woman" (lenition after a feminine singular noun)
- na fir mhóra "the big men" (lenition after a plural noun ending in a slender consonant)
- ainm an fhir bhig "the name of the small man" (lenition after a masculine singular noun in the genitive)
- sa chrann mhór "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.
|Radical||Eclipsed||Capitalized radical||Capitalized eclipsed|
|b /bˠ/, /bʲ/||mb /mˠ/, /mʲ/||B||mB|
|c /k/, /c/||gc /ɡ/, /ɟ/||C||gC|
|d /d̪ˠ/, /dʲ/||nd /n̪ˠ/, /nʲ/||D||nD|
|f /fˠ/, /fʲ/||bhf /w/, /vʲ/||F||bhF|
|g /ɡ/, /ɟ/||ng /ŋ/, /ɲ/||G||nG|
|p /pˠ/, /pʲ/||bp /bˠ/, /bʲ/||P||bP|
|t /t̪ˠ/, /tʲ/||dt /d̪ˠ/, /dʲ/||T||dT|
The other consonants do not change under eclipsis.
2. A vowel receives a preceding n- (pronounced /n̪ˠ/ before a, o, u, /nʲ/ before e, i). The hyphen is not used before a capital letter.
|Radical||Eclipsed||Capitalized radical||Capitalized eclipsed|
|a, á||n-a, n-á||A, Á||nA, nÁ|
|e, é||n-e, n-é||E, É||nE, nÉ|
|i, í||n-i, n-í||I, Í||nI, nÍ|
|o, ó||n-o, n-ó||O, Ó||nO, nÓ|
|u, ú||n-u, n-ú||U, Ú||nU, nÚ|
Environments of eclipsis
After plural possessive determiners
After certain numbers
The numbers that trigger eclipsis (the noun being in the singular) are:
- seacht gcapall "seven horses"
- ocht n-asal "eight donkeys"
- naoi gcat "nine cats"
- deich bpeann "ten pens"
Before a vowel in is written instead of i n-, though before the spelling reforms of the mid-20th century this was not the case.
Genitive plural nouns after the definite article
The genitive plural article na eclipses a following noun:
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 den, don, and sa(n), which trigger lenition). In southern dialects, t and d are also affected, and optionally s:
- ag an bhfear "by the man"
- ar an gcrann "on the tree"
- ar an doras (Connacht), ar an ndoras "on the door" (West)
A vowel-initial word is not affected after the definite article an.
After certain preverbal particles
- an poll a dtagann na coiníní as "the hole that the rabbits come out of"
- An dtagann sé gach lá? "Does he come every day?"
- Cá bhfuil mo spéaclaí? "Where are my glasses?"
- Dúirt sé go dtiocfadh sé. "He said that he would come."
- dá mbeadh a fhios sin agam "if I had known that"
A vowel-initial word is not affected after the interrogative particle an.
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 oíche "the night" (feminine singular nominative noun after definite article)
- an uisce "of the water" (masculine singular genitive noun after definite article)
- ó Albain "from Scotland" (noun after leniting preposition)
- seanathair "grandfather" (noun after preposed adjective: sean "old" + athair "father")
But where neither eclipsis nor lenition is expected, an initial vowel may acquire a prothetic t- or h- onset consonant.
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:
- an t-uisce "the water" (masculine singular nominative)
- an tÉireannach "the Irishman" (masculine singular nominative)
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 t-aon bhád ("the one boat")
- an t-ochtú bó ("the eighth cow")
- an t-aonú lá fichead (“the twenty-first day”)
The prothetic onset h- comes only when both the following conditions are met:
- a proclitic causes neither lenition nor eclipsis of consonants
- 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
- a haois (“her age”) (after possessive pronoun a (“her”))
- go hÉirinn (“to Ireland”) (after preposition go (“to, towards”))
- le hAntaine (“with Antaine”) (after preposition le (“with”))
- na hoíche (“of the night”) (on feminine singular genitive noun after definite article na)
- na héin (“the birds”) (on plural nominative/dative noun after definite article na)
- chomh hard le caisleán (“as high as a castle”) (after chomh (“as”) [xo])
- go hálainn (“beautifully”) (after adverbial particle go)
- Ná himigh uaim! (“Don’t leave me!”) (after negative imperative particle ná (“don’t”))
- an dara háit (“the second place”) (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:
- hinsíodh an scéal (“the story was told”)