Overview

Initial mutations are sound changes that affect the first letter of a word. They are a fundamental part of Irish grammar, triggered by the word that comes immediately before. The two most common mutations are lenition (séimhiú), which typically softens a consonant, and eclipsis (urú), which replaces the original consonant sound with a new one. Understanding when to use them is essential for speaking and writing Irish correctly.

The following table shows how the initial consonants of a word change when lenition or eclipsis is applied.

The consonants l, n, and r are never affected by lenition or eclipsis.

Lenition (An Séimhiú)

Lenition, known in Irish as séimhiú, is a “softening” of a consonant’s sound. In writing, it is marked by adding an h after the initial consonant. For example, b becomes bh, and c becomes ch.

Common Triggers for Lenition

Here are some of the most common situations that cause lenition.

The Definite Article an

Lenition occurs after the singular definite article an when it is followed by a feminine noun in the nominative case.

• an bhean - the woman (from bean, a feminine noun)
• an chathair - the city (from cathair, a feminine noun)

Possessive Pronouns

The possessive pronouns mo (my), do (your, singular), and a (his) all cause lenition.

• mo chat - my cat (from cat)
• do theach - your house (from teach)
• a mhadra - his dog (from madra)

Certain Prepositions

A number of simple prepositions cause lenition on the following noun. These include ar (on), de (from/off), do (to/for), faoi (under), ó (from), roimh (before), and trí (through).

• ar bhord - on a table (from bord)
• ó Chorcaigh - from Cork (from Corcaigh)

Numbers

The numbers aon (one) and dhá (two) cause lenition.

• aon teach amháin - one house (from teach)
• dhá chat - two cats (from cat)

The Vocative Case

The vocative particle a, used for direct address, causes lenition.

• A Sheáin! - Hello, Seán! (from Seán)
• A Mháire! - Hello, Máire! (from Máire)

Eclipsis (An tUrú)

Eclipsis, known in Irish as urú, involves “eclipsing” or covering the original initial sound of a word with a new sound. In writing, a new letter is placed before the original initial consonant. For example, b becomes mb, and c becomes gC.

Common Triggers for Eclipsis

Here are some of the most common situations that cause eclipsis.

The Preposition i

The preposition i (in) always causes eclipsis.

• i mBaile Átha Cliath - in Dublin (from Baile Átha Cliath)
• i nGaillimh - in Galway (from Gaillimh)

Possessive Pronouns

The possessive pronouns ár (our), bhur (your, plural), and a (their) all cause eclipsis.

• ár gcarr - our car (from carr)
• bhur dteach - your house (from teach)
• a mbád - their boat (from bád)

Numbers 7–10

The numbers seacht (seven), ocht (eight), naoi (nine), and deich (ten) cause eclipsis.

• seacht gcailín - seven girls (from cailín)
• deich mbád - ten boats (from bád)

After Certain Prepositions and the Article

When the definite article an follows certain prepositions, it causes eclipsis on the noun. This happens with prepositions like ar an, leis an, faoin, ón, and tríd an.

• ar an mbord - on the table (from bord)
• leis an bhfear - with the man (from fear)

Eclipsis of Vowels

When a word beginning with a vowel is eclipsed, an n- is prefixed to it.

• i nÉirinn - in Ireland (from Éirinn)
• ár n-athair - our father (from athair)

Other Initial Changes

Besides lenition and eclipsis, there are two other common changes to the start of a word: the h-prefix and the t-prefix.

The H-Prefix

An h is placed before a vowel in certain situations. This is sometimes considered a type of lenition but is often treated as a separate rule. A common trigger is the possessive pronoun a (her).

• a hainm - her name (from ainm)

It also occurs with the numbers three to six (trí, ceithre, cúig, sé).

• trí húll - three apples (from úll)

The T-Prefix

A t- is prefixed to masculine singular nouns that begin with a vowel after the definite article an.

• an t-uisce - the water (from uisce)
• an t-arán - the bread (from arán)

A t- is also prefixed to feminine nouns beginning with s after an in the nominative case. This t- prevents the s from being lenited.

• an tsráid - the street (from sráid)