There are actually quite a few classes of verbs, but Irish is much better at following their own rules than English is.

Most verbs in Irish are regular, and follow a very predictable form of conjugation. (As a matter of fact, there is a computer dictionary program for Irish that derives the conjugations of words based on their class -- you can find it here).

Verbs are usually referred to by their imperative forms (the command form -- such as sit). In addition, there are two main classes of verbs that make up a majority of the verb forms.

Class I verbs: end in -ann or -eann in the present tense
Class II verbs: end in -aíonn or -íonn in the present tense

Since the rules in Irish are actually more predictable than in English, it is relatively simple to determine the other forms of the verbs based on their present tense. Verbs in the past tense can be found by:

	Class I verbs	Class II verbs
ending	remove -eann or -ann	remove -íonn or -aíonn add -igh or -aigh
words beginning with consonants	lenition (not l, n ,r)	lenition (not l, n, r)
words beginning with vowels	add d'	add d'
words beginning with the letter f	lenition add d'	lenition add d'

Future tense verbs can be created by:

	Class I verbs	Class II verbs
endings	remove -eann or -ann add -faidh or -fidh	remove íonn or aíonn add -eoidh or -óidh
words beginning with consonants	no change	no change
words beginning with vowels	no change	no change
words beginning with the letter f	no chage	no change