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.
Not all words are subject to mutation. The only types of words subject to mutation are:
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”).
Consonants change as follows when they undergo lenition:
Radical | Lenited |
---|---|
b /bˠ/, /bʲ/ | bh /w/~/vˠ/, /vʲ/ |
c /k/, /c/ | ch /x/, /ç/ |
d /d̪ˠ/, /dʲ/ | dh /ɣ/, /j/ |
f /fˠ/, /fʲ/ | fh ∅ |
g /ɡ/, /ɟ/ | gh /ɣ/, /j/ |
m /mˠ/, /mʲ/ | mh /w/~/vˠ/, /vʲ/ |
p /pˠ/, /pʲ/ | ph /fˠ/, /fʲ/ |
s /sˠ/, /ʃ/ | sh /h/ |
t /t̪ˠ/, /tʲ/ | th /h/ |
Note: sc, sf, sm, sp, and st do not mutate and other consonants do not change under lenition.
After the definite article an and contractions of it with prepositions, e.g. don, ón:
The definite article triggers lenition of:
After the vocative particle a
After possessive determiners
The possessive determiners that trigger lenition are mo (“my”), do (“your (sg.)”), a (“his”)
After certain prepositions
After the preterite/conditional of the copula is, except in Northern Irish when the word starts with t, d and optionally s:
After preterite preverbal particles
After certain preverbal particles
A verb in the preterite, imperfect or conditional
These were originally preceded by the particle do and often still are in Munster.
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.
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.
After most prefixes
The second part of a compound
In these constructions coronals are lenited even following other coronals.
Genitive nouns in certain circumstances
Postposed adjectives in certain circumstances
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 |
The possessive determiners that trigger eclipsis are ár (“our”), bhur (“your (pl.)”), a (“their”)
The numbers that trigger eclipsis (the noun being in the singular) are:
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.
The genitive plural article na eclipses a following noun:
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:
A vowel-initial word is not affected after the definite article an.
A vowel-initial word is not affected after the interrogative particle an.
Vowel-initial words undergo eclipsis, as explained above, except after an.
A vowel-initial word does not change where lenition is expected:
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:
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:
The prothetic onset h- comes only when both the following conditions are met:
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
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: