How do you form the simple future tense?

In French, they are three groups of verbs, verbs that end in -er (eg manger), verbs that end in -ir (finir), and verbs that end in -re, -oir, or -ir (faire, pouvoir, or devenir). The verb endings are the same for all verb groups in the simple future tense: ai, as, a, ons, ez, ont.In general, in the first and second group, you just add that ending onto the verb when it is not conjugated, for example, je mangerai plus tard.There are some exceptions in the first group with verbs ending with -yer, -eler and -eter.In the third group, the future is almost as easy: you add on the verb endings, however, as always there are some exceptions. Verbs ending with a -e for example rire lose that 'e' when it is conjugated in the future tense, for example il rira (he will laugh). Some verbs ending in -ir in the third group lose their 'i' and there are also some changes to the future tense for verbs such as etre, avoir and aller.