"The men's cats"
Translation:Cait na bhfear
To be exact, the eclipsis is caused by the definitive article preceding the genitive noun. If the noun and the article were in the nominative case, on the other hand, no ecclipsis would be caused. Since both npl. and gpl. of the definite article are "na", we can only recognize the genitive by recognizing the ecclipsed noun.
I researched the genitive case a little bit, but what I found was broad, not specific to Irish.
Is the general rule for Irish the mutation of a singular to a plural form and vice versa, when in the genitive case? Are there exceptions to the rule?
I am on the app, so no "tips" section. Is there a good resource for learning Irish grammar?
No, "the mutation of a singular to a plural form and vice versa" is not the General rule. Nouns are divided into 5 declensions and the rules for genitive formation depend on the declension. Most 1st declension nouns form the nominative plural and the genitive singular in the same way. fear is a 1st declension noun.