Declension

Irish cardinal numbers can be treated as nouns and declined with the definite article. This page shows their forms in the nominative, genitive, and plural cases.

Numbers Nouns Declension Article

When used on their own without a following noun, Irish cardinal numbers act like regular nouns. They have a gender and can be declined with the definite article, an. All numbers are treated as masculine nouns except for náid (zero), which is feminine.

These forms are used to refer to the number itself, but also for things like bus routes, decades, or playing cards.

Tóg an seacht. - Take the number seven (bus).
Ba iad na nóchaidí an ré órga. - The nineties were the golden era.
Tarraing an deich hart. - Draw the ten of hearts.

Declension Forms

The table below shows the main declined forms for numbers when used with the definite article.

Number	Nominative Singular	Genitive Singular	Nominative Plural
0	`an náid`	`na náide`	`na náideanna`
1	`an t-aon`	`an aoin`	`na haonta`
2	`an dó`	`an dó`	`na dónna`
3	`an trí`	`an trí`	`na tríonna`
4	`an ceathair`	`an cheathair`	`na ceathaireanna`
5	`an cúig`	`an chúig`	`na cúigeanna`
6	`an sé`	`an tsé`	`na séanna`
7	`an seacht`	`an tseacht`	`na seachtanna`
8	`an t-ocht`	`an ocht`	`na hochtanna`
9	`an naoi`	`an naoi`	`na naonna`
10	`an deich`	`an deich`	`na deicheanna`
11	`an t-aon déag`	`an aoin déag`	`na haonta déag`
12	`an dó dhéag`	`an dó dhéag`	`na dónna déag`
13	`an trí déag`	`an trí déag`	`na tríonna déag`
20	`an fiche`	`an fhichead`	`na fichidí`
21	`an fiche a haon`	`an fhichead a haon`	`na fichidí a haon`
30	`an tríocha`	`an tríochad`	`na tríochaidí`
40	`an daichead`	`an daichid`	`na daichidí`
40	`an ceathracha`	`an cheathrachad`	`na ceathrachaidí`
50	`an caoga`	`an chaogad`	`na caogaidí`
60	`an seasca`	`an tseascad`	`na seascaidí`
70	`an seachtó`	`an tseachtód`	`na seachtóidí`
80	`an t-ochtó`	`an ochtód`	`na hochtóidí`
90	`an nócha`	`an nóchad`	`na nóchaidí`
100	`an céad`	`an chéid`	`na céadta`
1,000	`an míle`	`an mhíle`	`na mílte`
1,000,000	`an miliún`	`an mhilliúin`	`na milliúin`

The genitive plural is typically formed by eclipsing the nominative plural form, for example, na gceathaireanna (of the fours) or na bhfichidí (of the twenties).