An bhfuil riail faoi leith ann chun gach focal a chur sa tuiseal ginideach? Tá. Tá cúig riail (ar a laghad!). Nouns in Irish are divided into 5 groups, or declensions, according to how they form the genitive case. - Declension 1: consists of masculine nouns ending in a broad consonant, they form their genitive by slenderising the final consonant, usually by adding an "i" before it, e.g. cat > cait; leabhar > leabhair; fear > fir (includes all nouns ending in "-án"). - Declension 2: mostly feminine nouns (except "im" and "sliabh", which are masculine) ending in a consonant, they form the genitive by adding a final "-e" and slenderising a preceding consonant where necessary, e.g. fuaim > fuaime; cáis > cáise; fuinneog > fuinneoige; ciall > céille (includes all nouns ending in "-óg", "-eog", "-lann"). - Declension 3: masculine or feminine nouns ending in a consonant which form their genitive by adding "-a" and broadening the final consonant where necessary, e.g. gleann > gleanna; dochtúir > dochtúra; beannacht > beannachta (includes nouns ending in "-acht", "-éir", "-óir", "-úir", "-áil"). - Declension 4: nouns ending in "-ín" or in a vowel, and a few others, they don-t change in the genitive, e.g. muinín > muinín; file > file; ainmhí > ainmhí; baile > baile. - Declension 5: nouns ending in a slender consonant or a vowel, the genitive case ends in a broad consonant but there are many different ways of forming it, e.g. "-ach": cáin > cánach; cathair > cathrach; riail > rialach "-n": ceathrú > ceathrún; comharsa > comharsan; monarcha > monarchan "-d": fiche > fichead; cara > carad broadening: athair > athar; máthair > máthar; abhainn > abhann; namhaid > namhad; Nollaig > Nollag Then there are also some irregular nouns which form their genitive case in other ways: deoch > dí; teach > tí; lá > lae; leaba > leapa; mí > míosa; bean > mná. As you can see, it's very simple;)