Third Declension

Learn how to form the cases and plurals of masculine and feminine nouns belonging to the third declension in Irish.

Nouns Grammar Declension Cases

The third declension includes both masculine and feminine nouns that end in a consonant, which can be either broad or slender. This declension is characterised by a genitive singular ending in -a and a variety of strong plural endings.

Genitive Singular

The genitive singular is typically formed by adding -a. The process differs slightly depending on the final consonant of the noun.

Nouns ending in a broad consonant

For nouns ending in a broad consonant, simply add the ending -a.

beannacht (a blessing) → beannachta
áth (a ford) → átha

Nouns ending in a slender consonant

For nouns ending in a slender consonant, the final consonant is first made broad (a process called depalatalisation), and then -a is added.

feoil (meat) → feola
cuid (a part, a share) → coda
fuil (blood) → fola
mil (honey) → meala

Nouns ending in -int

For nouns with the ending -int, the final -t is dropped before adding the genitive ending -a.

canúint (a dialect) → canúna

Nouns ending in -irt

For nouns ending in -irt, the -t changes to -th- before the -a is added.

imirt (playing, a game) → imeartha

Plural Forms

While older forms exist, modern Irish almost exclusively uses strong plural endings for the third declension.

Historical note on weak plurals

Older grammar books often describe a weak plural ending in -a as the main form for this declension. This is now rare. In these cases, the genitive plural is formed by dropping the -a from the nominative plural.

béas (a habit) → plural béasa, genitive plural béas
dreas (a turn, a spell) → plural dreasa, genitive plural dreas Nouns with a vowel change in the genitive singular, like fuil (blood) becoming fola, also sometimes use this -a plural.

In modern Irish, the following strong plural patterns are common.

Nouns for people and agents

Nouns ending in -aeir, -éir, -eoir, -óir, or -úir (often denoting people or agents) form their plural by adding -í.

Gaeilgeoir (an Irish speaker) → Gaeilgeoirí
dochtúir (a doctor) → dochtúirí

Abstract nouns

Nouns ending in -acht or -íocht are typically feminine and form their plural by adding -aí.

Gaeltacht (an Irish-speaking area) → Gaeltachtaí
mallacht (a curse) → mallachtaí

Monosyllabic masculine nouns

Many masculine, single-syllable nouns take the ending -anna or -aí.

loch (a lake) → lochanna
rud (a thing) → rudaí

Nouns ending in -l, -n, or -r

Nouns ending in -l, -n, or -r have several possible plural endings.

The ending -acha is common, often after making the final consonant broad: barúil (an opinion) → barúlacha.
The ending -ta is also used, especially for nouns ending in -l or -n: bliain (a year) → blianta.
The ending -te is a less common alternative: móin (peat, turf) → móinte.

Common Endings and Patterns

Many nouns in the third declension follow predictable patterns based on their endings. This table summarises the most common ones.

Ending	Gender	Genitive Singular	Plural
`-áil`	m/f	`-ála`	`-áilí`
`-(a)íl`	m/f	`-(a)íola`	`-(a)ílí`
`-óir`	m	`-óra`	`-óirí`
`-eoir`	m	`-eora`	`-eoirí`
`-úir`	m	`-úra`	`-úirí`
`-aeir`	m	`-ara`	`-aeirí`
`-éir`	m	`-éara`	`-éirí`
`-irt`	f	`-artha`	`-airtí`
`-áint`	f	`-ána`	`-áintí`
`-úint`	f	`-úna`	`-úintí`
`-acht`	f	`-achta`	`-achtaí`
`-íocht`	f	`-íochta`	`-íochtaí`

Examples of 3rd Declension Nouns

The following table shows the full declension for a range of common nouns, including the initial mutations that occur after the definite article an or na.

Nominative Singular	Genitive Singular	Nominative Plural	Genitive Plural	Translation
`an béas`	`an bhéasa`	`na béasa`	`na mbéas`	the habit
`an tréad`	`an tréada`	`na tréada`	`na dtréad`	the herd
`an rud`	`an ruda`	`na rudaí`	`na rudaí`	the thing, the object
`an t-am`	`an ama`	`na hamanna`	`na n-amanna`	the time
`an loch`	`an locha`	`na lochanna`	`na lochanna`	the lake
`an troid`	`na troda`	`na troideanna`	`na dtroideanna`	the fight
`an droim`	`an drama`	`na dromanna`	`na ndromanna`	the back
`an greim`	`an ghreama`	`na greamanna`	`na ngreamanna`	the grip, the hold, the bite
`an buachaill`	`an bhuachalla`	`na buachaillí`	`na mbuachaillí`	the boy
`an dochtúir`	`an dochtúra`	`na dochtúirí`	`na ndochtúirí`	the doctor
`an saighdiúir`	`an tsaighdiúra`	`na saighdiúirí`	`na saighdiúirí`	the soldier
`an múinteoir`	`an mhúinteora`	`na múinteoirí`	`na múinteoirí`	the teacher
`an táilliúir`	`an táilliúra`	`na táilliúirí`	`na dtáilliúirí`	the tailor
`an Cháisc`	`na Cásca`	`na Cáiscí`	`na gCáiscí`	Easter
`an chanúint`	`na canúna`	`na canúintí`	`na gcanúintí`	the dialect
`an leann`	`an leanna`	`na leannta`	`na leannta`	the beer
`an gleann`	`an ghleanna`	`na gleannta`	`na ngleannta`	the valley
`an bhliain`	`na bliana`	`na blianta`	`na mblianta`	the year
`an fheoil`	`na feola`	`na feolta`	`na bhfeolta`	the meat
`an mhóin`	`na móna`	`na móinte`	`na móinte`	the peat
`an mhaitheas`	`na maitheasa`	-	-	the goodness
`an tSamhain`	`na Samhna`	`na Samhnacha`	`na Samhnacha`	November, 1st November
`an gamhain`	`an ghamhna`	`na gamhna`	`na ngamhna`	the calf
`an bhanríon`	`na banríona`	`na banríonacha`	`na mbanríonacha`	the queen
`an fhuil`	`na fola`	`na fola`	`na bhfola`	the blood
`an mhuir`	`na mara`	`na mara`	`na mara`	the sea
`an sioc`	`an tseaca`	-	-	the frost