Initial Mutation: After the Article
The article in Classical Modern Irish generally behaves the same way as it does in today’s standard Irish, but it differs especially in the accusative and dative singular.
Masculine Singular Nouns After the Article
| nominative | (as in today’s Irish) an t- before a vowel, but otherwise unchanged and not mutating what follows it |
A-tá an fear / an file / an t-asbal / an sluagh san tigh. |
| accusative | an + eclipsis of eclipsable consonants (or, when the object of a verb and not inflected and not preceded by a preposition can be treated as though nominative) |
Direct object of verb: Mol an bhfear (or, as though in the nominative, Mol an fear). Mol an bhfilidh (but not *an filidh, because the noun is inflected). Mol an asbal (or an t-asbal). Mol an sluagh. After accusative-governing preposition: |
| genitive | (as in today’s Irish) an + lenition of lenitable consonants (including lenition of s by t) |
Teach an fhir / an fhileadh / an asbail / an tsluaigh. |
| dative | an + lenition of lenitable consonants (including lenition of s by t) |
don fhior / don fhilidh / don asbal / don tsluagh |
Feminine Singular Nouns After the Article
| nominative | (as in today’s Irish) an + lenition of lenitable consonants (including lenition of s by t) |
A-tá an bhó / an adharc / an tsleagh agam. |
| accusative | an + eclipsis of eclipsable consonants | Mol an mboin / an adhairc / an sleigh |
| genitive | (as in today’s Irish) na + h before a vowel (but no change to consonants) |
Dath na bó / na hadhairce / na sleighe |
| dative | an + lenition of lenitable consonants (including lenition of s by t) |
don bhoin / don adhairc / don tsleigh |
Plural Nouns (Masculine and Feminine) After the Article
| genitive | (as in today’s Irish) na + eclipsis of eclipsable letters |
méad na bhfear/ na bhfileadh / na n-asbal / na sluagh / na mbó / na n-adharc / na sleagh |
| nominative, accusative, and dative |
(as in today’s Irish) na + h before a vowel (but no change to consonants) |
(nominative:) A-táid na fir / na filidh / na hasbail / na sluaigh / na ba (or na baoi) / na hadharca / na sleagha san tigh. (accusative:) Mol na fiora / na fileadha / (dative:) do na fearaibh / do na fileadhaibh / |