The three verb groups
Summary
French verbs are traditionally sorted into three groups by their infinitive ending and how regularly they conjugate: -er (group 1), -ir with -iss- (group 2), and everything irregular (group 3).
Explanation
French conjugation is organised around three traditional groups, defined by the infinitive ending and by how predictably the verb changes. Group 1 is every verb ending in -er except aller, all of which follow one regular model such as parler; it is by far the largest group and covers roughly nine out of ten French verbs, including almost every new verb coined today. Group 2 is the regular -ir verbs that insert -iss- in their plural forms, like finir (nous finissons). Group 3 is the closed set of irregular verbs: the -ir verbs without -iss- (partir, venir), all verbs in -re (prendre, dire) and -oir (vouloir, voir), and the irregular aller.
The grouping describes the shape of the ending, not the meaning of the verb. A useful consequence is that once you know the group, you usually know the whole conjugation: group 1 and group 2 are fully predictable, so learning their two patterns lets you conjugate thousands of verbs. Group 3, by contrast, is not really a single pattern but a collection of frequent verbs that must be learned individually, even though several smaller families (such as -dre verbs like attendre) recur within it.
When is the distinction useful? Constantly, because the group tells you which present-tense endings to use and which stem to build on. It also feeds many other tenses: the present stem of a regular verb gives you the imperative and, via the ils-form, the present subjunctive. Knowing that a verb is group 3 is itself information: it warns you that its stem may change between singular and plural (je viens / nous venons) and that you should check, not guess.
The main pitfall is judging the group by the infinitive ending alone. An -ir ending does not guarantee group 2: only verbs that take -iss- (finir, choisir, grandir) belong there, while partir, sortir, dormir, ouvrir and venir are group 3 and never take -iss-. Likewise, aller looks like an -er verb but is irregular. A reliable test is the present participle: group 2 verbs end in -issant (finissant), group 3 -ir verbs do not (partant).
Rule of thumb: assume a verb in -er is regular group 1 (only aller is the exception), test an -ir verb by asking whether it takes -iss- in the plural, and treat every -re and -oir verb — and any -ir verb without -iss- — as group 3 to be looked up rather than guessed.
Examples
Parler, finir et prendre appartiennent chacun à un groupe différent. — Parler, finir and prendre each belong to a different group.
Le verbe finir prend -iss- au pluriel : nous finissons. — The verb finir takes -iss- in the plural: nous finissons.
Aller se termine par -er mais reste irrégulier : je vais. — Aller ends in -er but stays irregular: je vais. (An -er ending does not always mean group 1.)
Partir finit par -ir mais ne prend pas -iss- : nous partons. — Partir ends in -ir but does not take -iss-: nous partons. (partir is group 3, not group 2.)
Les verbes en -re comme prendre sont du troisième groupe. — Verbs in -re like prendre are in the third group.
Common mistakes
Nous partissons demain.
Nous partons demain.
Partir is a group 3 -ir verb that does not take -iss-; that infix belongs only to regular group 2 verbs like finir (nous finissons). Partissons wrongly copies the group 2 pattern onto partir; the correct nous form is partons, built on the short stem part-.
Related rules
verb-groupspresent-tenseregular-verbsirregular-verbs