Irish initial mutations


, like all modern Celtic languages, is characterized by its initial consonant mutations. These mutations affect the initial consonant of a word under specific morphological and syntactic conditions. The mutations are an important tool in understanding the relationship between two words and can differentiate various meanings.
Irish, like Manx and colloquial Scottish Gaelic, uses two mutations on consonants: lenition and .
Originally these mutations were phonologically governed external sandhi effects: lenition was caused by a consonant being between two vowels, and eclipsis when a nasal preceded an obstruent, including at the beginning of a word.
There are also two mutations, t-prothesis and h-prothesis, found on vowel-initial words.
See Irish phonology for a discussion of the symbols used on this page.

Lenition (''séimhiú'')

Effects of ''séimhiú''

  1. A stop becomes a fricative. Voicing is retained, as is place of articulation except with the coronals.
  2. * →
  3. * →
  4. * →
  5. * →
  6. * →
  7. * →
  8. * →,
  9. * →
  10. * →
  11. * →
  12. * →
  13. * →
  14. becomes or ; becomes.
  15. and become ; but,,,,, and do not mutate.
  16. and are deleted.
Séimhiú is symbolized in the orthography by an h following the consonant in question or, in some older typefaces and texts, by a dot above the letter that has undergone lenition.
The other consonants do not change under lenition.

Environments of séimhiú

After proclitics

;After the definite article
The definite article triggers lenition of:
  1. a feminine noun in the nominative singular
  2. :an bhean "the woman"
  3. a masculine noun in the genitive singular
  4. :an fhir "of the man" e.g. carr an fhir, the man's car
  5. a noun in the dative singular, when the article follows one of the prepositions de "from", do "to" or i "in"
  6. :do + an = don: don fhear "to the man"
  7. :de + an = den: den bhean "from the woman"
  8. :i + an = sa: sa chrann "in the tree"; san fhómhar "in the autumn"
;After the vocative particle a
;After possessive pronouns
The possessive pronouns that trigger lenition are mo "my", do "your ", a "his"
;After certain prepositions
;After the preterite/conditional of the copula
;After the 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.
in these constructions if two coronals are adjacent.
;After certain numbers
The singular form is used after numbers and is lenited in the following cases:
;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
;Postposed adjectives in certain circumstances

Effects of ''urú''

The following tables show how eclipsis affects the start of words. Eclipsis is symbolised in the orthography by adding a letter—or occasionally two letters—to the start of the word. If the word is to be capitalised, the original first letter is capitalised, not the letter or letters added for eclipsis. An example is the "F" in Ireland's national anthem, Amhrán na bhFiann.
1. A voiceless stop or is voiced:
Sound changeNormalUrúGloss
→ práta bpráta "potato"
→ peann bpeann "pen"
→ tráta dtráta "tomato"
→ teanga dteanga "tongue"
→ cat gcat "cat"
→ ceann gceann "head"
→, focal bhfocal "word"
→ freagra bhfreagra "answer"

In the West Muskerry dialect, and are also voiced, but this is not reflected in the orthography nor is it standardised outside of that barony.
2. A voiced stop becomes a nasal:
Sound changeNormalUrúGloss
→ bainne mbainne "milk"
→ bean mbean "woman"
→ droim ndroim "back"
→ dinnéar ndinnéar "dinner"
→ glúin nglúin "knee"
→ geata ngeata "gate"

3. A vowel receives a preceding or . However, a vowel-initial word is not affected after the definite article an.
Sound changeNormalUrúGloss
→ éan n-éan "bird"
→ oíche n-oíche "night"

The other consonants do not change under urú.

Environments of urú

After plural possessive pronouns

The possessive pronouns that trigger eclipsis are ár "our", bhur "your ", a "their"
Note that a can mean "his", "her" or "their", but these different uses can still be distinguished, since a causes lenition when used as "his", causes eclipsis when used as "their", and neither when used as "her".

After certain numbers

The numbers that trigger eclipsis are:
Before a vowel in is written instead of i n-.
The genitive plural article na eclipses a following noun:
In western and southern dialects, nouns beginning with a noncoronal consonant are eclipsed after combinations of preposition + article in the singular
A vowel-initial word does not change if a séimhiú is expected:
However, if neither urú nor séimhiú is expected, an initial vowel may acquire a prothetic onset consonant. For example, a vowel-initial masculine singular nominative noun requires a t- after the definite article:
Otherwise, there is the prothetic onset h, which 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.
Examples of h-prothesis