Catalan verbs are traditionally divided into three conjugations, with vowel themes -a-, -e-, -i-, the last two being split into two subtypes. However, this division is mostly theoretical. Only the first conjugation is nowadays productive (with about 3500 common verbs), whereas the third (the subtype of servir, with about 700 common verbs) is semiproductive. The verbs of the second conjugation are fewer than 100, and it is not possible to create new ones, except by compounding.

How are Catalan verbs grouped?