Used before nouns;dó is used when free-standing (counting, telling a row of numerals, etc). The following noun is in thesingularnominative (or, in the few cases where distinctduals have survived, the dual nominative (e.g.dhá bhróig – "two shoes")) and is almost alwayslenited; one exception is with the third-person possessive determinera, which triggers mutation as if thedhá simply was not there:
Exceptionally, the wordtrian(“third”) undergoeseclipsis afterdhá:
dhádtrian ―two thirds
When used with adjectives, the adjective is always in the nominative plural and is lenited by default:
dhá bhádmhóra ―two big boats
dhá mhadradhubha ―two black dogs
dhá amhránghearra ―two short songs
The alternative formdá is used after the definite article (which is always in the singular and is alwaysan, even with feminine nouns in the genitive),aon ("any"), andcéad ("first"):
andá leabhar ―the two books
teangachaan dá thír ―the two countries' languages
aondá áit ―any two places
an chéaddá bhliain ―the first two years
When referring to human beings, the personal formbeirt is used.
