Lenition (Séimhiú)

How the lenition/séimhiú works in Irish

Nativlang’s video on the origin of mutations in Irish.

What is lenition? (séimhiú)

A common feature across all Celtic languages is the idea of mutations. A mutation is a linguistic phenomenon where the initial consonant in a given word changes or mutates.

In Irish, mutations can be caused by certain words such as prepositions (words like on, with, to, for, etc.), possessive pronouns (my, your, his, her), the masculine and feminine or adjective agreement. On the right you can see an amazing video by Nativlang explaining its origins!

There are two types of mutation in Irish: lenition (or séimhiú as it’s called in Irish) and eclipsis (or urú as it’s called in Irish). This article focuses on the séimhiú.

Lenition (séimhiú) is a change in the initial consonant sound in a word which is marked by adding a h after the first letter in the word. Here are some examples of word being changed using lenition.

Original Word

b

c

d

f

g

m

p

s

t

buachaill

cat

doras

fear

garda

mála

póg

seomra

teach

bh

ch

dh

fh

gh

mh

ph

sh

th

Lenited Word

bhuachaill

chat

dhoras

fhear

gharda

mhála

phóg

sheomra

theach

Change in Pronunciation (Broad / Slender)

bh = w / vʲ

ch = x / ç

dh = ɣ / j

f = ø (silent letter)

g = ɣ / j

mh = w / vʲ

ph = fˠ / fʲ

sh = h

th = h

For notes on pronunciation or help with the IPA, be sure to check the pronunciation section.

Additional Notes

d, t, s

Note that in Irish, when DENTAL sounds come together, lenition cannot occur. (This isn’t the case for adjectives).

  • sa teach (not sa theach)

  • an duilleog (not an dhuilleog)

sc, sp, st, sm

  • these combinations never lenite because they would be too difficult to pronounce!

f

  • sometimes, if the change in the word is too drastic we avoid leniting the letter f (full article coming on this soon)!

b, p

note that b and p will often avoid lenition after the letter m.

  • um bosca

  • um póg

l, n, r

  • note that l, n and r DO lenite in speech but it isn’t represented in writing (see the article on this here).

When to use lenition:

Note that this list is best used for reference, especially for beginner-intermediate learners. It’s usually best to learn the rules for lenition as you learn the language itself! This list is also not completely exhaustive and certain exceptions and specific rules are given in their respective grammar sections.

For nouns:

  • after the vocative particle a: a Cháit, a Shinéad, a Sheáin

  • feminine nouns in the nominative preceeded by the definite article: an bhean, an Ghaeilge

  • masculine nouns in the genitive preceeded by the definite article: an chait, an mhadra

  • words in the genitive attached to feminine nouns (with some exceptions): bean chéile, tine mhóna

  • names or placenames in the genitive: teaghlach Cháit, ollscoil Chorcaí

  • linking double genitives: bean chomharsa mo mháthar

  • after the numbers 1-6: dhá bhosca, ceithre theach, sé chapall

  • after beirt/dís: beirt mhac, dís mhúinteoirí

  • after an chéad: an chéad chaibidil

  • after mo, do and a (his): mo chara, do chara, a chara

  • after the prepositions ar, ó, do, de, faoi, idir (between), mar (as), roimh, trí, gan

  • after the prepositions don and den

  • after the preposition sa(n)

  • after uile or chuile

  • in surnames after Uí, Ní, Mhic, Nic

For verbs:

  • after the negative particle ní: ní thosaíonn, ní bheidh

  • after the verbal particles ending in -r: ar, gur, nár, níor, murar,

  • after the direct relative particle a (who, which): an duine a fhoghlaimíonn an Ghaeilge

  • after má (if)

  • for verbs in the past tense: bhí, chaith, dhún

  • for verbs in the conditional: bheadh, chaithfeadh, dhúnfadh

  • for verbs in the past habitual: bhíodh, chaitheadh, dhúnadh

  • the infinitive with the particle a: rud a dhéanamh, rud a fheiceáil, rud a chaitheamh

For adjectives:

  • adjectives after a feminine noun: bean dheas, bileog bhán

  • adjectives after a masculine genitive noun: an phinn ghoirm, an leabhair shuimiúil

  • adjectives after a slender plural: fir dheasa, mic chliste

  • 1-19 + noun + adjective: na seacht mbosca mhóra

  • beirt + noun + adjective: beirt pháistí bheaga

Miscellaneous:

  • after an- (very)

  • in compound words: scoilbhliain, ollmhargadh

  • déag lenites after a dó or nouns ending in a vowel: a dó dhéag, dhá hata dhéag