Appendix:Irish adjectives

Irish adjectives have three declensions, each with the same case structure as the nouns (nominative, vocative, genitive, dative). The adjectives agree with nouns in case, plurality[1] and gender.[2]

The three declensions are classified by their endings: consonants; ‑úil, ‑ir; vowels. The genitive singular forms are analogous to noun declension forms:

  • 1st-masculine to noun-1st (slenderise)
  • 1st-feminine to noun-2nd (+ e[3])
  • 2nd-feminine[4] to noun-3rd (+ a)
  • 3rd to noun-4th (unchanged).

Plurals are generally formed with the suffix ‑a. They are considered weak or strong according to the noun they qualify, and the same rule applies to the genitive plural: when weak, it is the same as the nominative singular; when strong, it is the same as the nominative plural.

Syncopation occurs in some first declension adjectives in the genitive singular feminine, and plural. Many such plurals retain the genitive's slender form in + e.

The comparative (and superlative) is formed regularly using the genitive singular feminine. There is a small set of irregular comparatives.

Irish adjectives undergo initial mutation, by lenition only.[5] In the singular, agreement follows the pattern[6] of the qualified noun. In the plural, there is in general no lenition.[7] Any lenition occurs across all qualifying adjectives.[8] The dentals rule does not apply.[9]

Quick reference table

1st 2nd 3rd
Gender m f m f m & f
Singular Nom consonant ‑úil, ‑ir vowel
Voc slender - - -
Gen slender [10] + e - + a -
Dat - slender [11] - -
Weak Plural Noun Nom + a/e[12] + a -
Voc + a + a -
Gen - - -
Dat + aibh [13] + aibh -
Strong Plural Noun Nom + a + a -
Voc + a + a -
Gen + a + a -
Dat + aibh [13] + aibh -

First declension


Irish first declension adjectives end in consonants (other than the second declension ‑úil and ‑ir).

The genitive singular masculine (gsm) is formed in general by slenderising, although there are exceptions (and exceptions to the exceptions). The genitive singular feminine (gsf) form is analogous to the noun second declension, that is, with suffix ‑e. The plural in general is formed with suffix ‑a, but the genitive obeys the weak/strong rule in agreement with the noun qualified.

Adjectives whose gsm is not slenderised are [14]:

The gsf of (polysyllabic) adjectives ending in ‑ach is written ‑aí < aighe.

Plurals in + e


Slender adjectives have natural plurals in + e, e.g., ait, npl aite, maith, npl maithe.



When forming first declension genitive singular feminine, and plurals, unstressed vowels are often syncopated.

  • folamh, gsf, cmp foilmhe (not *folaimhe), npl folmha
  • ramhar, gsf, cmp raimhre, npl ramhra

A couple of nouns are not syncopated in the genitive, but are in the plural.

  • bodhar, gsf, cmp bodhaire, npl bodhra
  • sleamhain, gsf, cmp sleamhaine, npl sleamhna

If the root is slender, the plural may remain slender.

  • íseal, gsf, cmp, npl ísle
  • láidir, gsf, cmp, npl láidre
  • Exceptions (root is broad, but plural is + e) include:

An extreme case is álainn, which loses the whole syllable:

  • álainn, gsf, cmp, npl. áille.

Declension tables

mór (big) Singular Weak Plural [15]
m f m & f
Nom mór mhór móra
Voc mhóir mhór móra
Gen mhóir ire mór
Dat mór mhór móra
fliuch (wet) Singular Weak Plural [15]
m f m & f
Nom fliuch fhliuch fliucha
Voc fhliuch fhliuch fliucha
Gen fhliuch fliche fliuch
Dat fliuch fhliuch fliucha
ramhar (fat) Singular Weak Plural [15]
m f m & f
Nom ramhar ramhar ramhra
Voc ramhair ramhar ramhra
Gen ramhair raimhre ramhar
Dat ramhar ramhar ramhra

Second declension


Irish second declension adjectives end in ‑úil and ‑ir.

The genitive singular masculine (gsm) of second declension adjectives, being already slender, is the same as the nominative singular. The genitive singular feminine (gsf) form is analogous to the noun third declension, that is, with suffix ‑a. The plural in general is formed with suffix ‑a, but the genitive obeys the weak/strong rule in agreement with the noun qualified.

The adjectives in ‑úil are derived from (s)amhail.[16]

The adjectives in ‑ir are syncopated when adding the suffix ‑a, for example, deacair, gsf, npl. deacra.

Declension tables

suimiúil (interesting) Singular Weak Plural [15]
m f m & f
Nom suimiúil shuimiúil suimiúla
Voc shuimiúil shuimiúil suimiúla
Gen shuimiúil suimiúla suimiúil
Dat suimiúil shuimiúil suimiúla
deacair (difficult) Singular Weak Plural [15]
m f m & f
Nom deacair dheacair deacra
Voc dheacair dheacair deacra
Gen dheacair deacra deacair
Dat deacair dheacair deacra

Third declension


Irish third declension adjectives end in vowels.

There are no changes to third declension adjective endings.[17]

Declension table

crua (hard) Singular Weak Plural [15]
m f m & f
Nom crua chrua crua
Voc chrua chrua crua
Gen chrua crua crua
Dat crua chrua crua

Irregular adjectives


There are very few irregular adjectives in Irish. The irregular forms get reused for the comparative.

  • breá (pretty), gsm. breá, gsf. breá, npl. breátha
  • gearr (short), gsm. gearr, gsf. giorra, npl. gearra
  • te (hot), gsm. te, gsf. te, npl. teo

Irregular comparatives


Comparatives are formed regularly by using the genitive singular feminine (gsf) form.

There are a few irregular comparatives. A small subset has different sources than the radical:

Fada has both irregular and regular variants:

  • fada (long), cmp. sia
  • fada (long), cmp. faide

The irregular adjectives use their irregular form:

  • breá (pretty), cmp. breátha
  • gearr (short), cmp. giorra
  • te (hot), cmp. teo

Others have irregular variants:

  • dócha (likely), cmp. dóichí
  • fogas (close), cmp. foisce
  • furasta (simple), cmp. fusa
  • mór (big), cmp. mó
  • tirim (dry), cmp. tirime, tiorma
  • tréan (strong), cmp. tréise, tréine

There is also a couple of defective adjectives, with comparatives only:

Wiktionary templates



  1. ^ There is no trace of dual forms. After ordinals, adjectives are plural (and lenited after 2—6), e.g. dhá úll mhóra
  2. ^ Usually cited in that order, e.g. genitive singular feminine (also in Irish, ginideach uatha baininscneach)
  3. ^ Slenderise if necessary
  4. ^ 2nd-masculine adjectives, being slender, are unchanged in form
  5. ^ Eclipsis does not occur
  6. ^ Gender, case, prepositional
  7. ^ Two notable exceptions, when qualifying: weak slenderised plurals of the first declension, na cait mhóra; nouns of singular form after leniting cardinals, dhá chat mhóra
  8. ^ e.g. an bhean bheag fhionn
  9. ^ e.g., an bhean dheas
  10. ^ A significant sub-category of first declension adjectives may not be slenderised
  11. ^ Considered archaic/dialectical, but see, e.g., lámh and other Irish nouns with slender dative singular forms
  12. ^ slender adjectives, and especially after syncopation.
  13. 13.0 13.1 Archaic
  14. ^ The Official Standard, An Caighdeán Oifigiúil, 2017
  15. 15.0 15.1 15.2 15.3 15.4 15.5 Lenition when qualifying weak, slenderised first declension plurals, and singular-form nouns after cardinals, is not shown
  16. ^ cf. English -ly, German -lich
  17. ^ Initial mutations do occur where necessaary

See also