In French, verbs can be grouped into three different categories called groups.
FIRST GROUP: all verbs when INFINITIVE is finished by -ER except ALLER.
Particularity: this is the most regular group because the radical does not change during the conjugation: AIMER: aim-e; aim-ons; aim-ent).SECOND GROUP: all verbs finished by -IR (verbs with infinitive in -IR and present participle in -ISSANT).
This is a regular group. Those verbs always use a double radical. One for the singular and the second one for plural persons: fin-is; finiss-ons).THIRD GROUP: here are all the irregular verbs. Can be divided into three main sub-category:
1. verbs in -IR (like MOURIR: mour-ant; mour-ons);
2. verbs in -OIR (like RECEVOIR: recev-ant; recev-ons);
3. verbs in -RE (like RENDRE: rend-ant; rend-ons);
4. ALLER even if it terminated by -ER