Conjugations
There are four conjugations in Latin which define patterns of verb inflection. However the grouping in conjugations is based solely on the behaviour of the verb in the present system, and the stems for other forms cannot be inferred from the present stem, so several forms of the verb are necessary to be able to produce the full range of Latin verbal forms. Most Latin verbs belong to one of the four verb conjugations, though some, like esse (to be), do not.
Read more about this topic: Latin Conjugation