How to conjugate irregular French verbs

On the previous page, we saw that irregular French verbs can be categorised according to four main verb features: their 'characteristic consonant' (if any), vowel change (if any), future stem (if irregular) and past participle form (often arbitrary). Now we'll see how to put this information to use in order to form irregular verbs in the different tenses.

Present tense

The present tense is the most complex. The first stage is to work out the stem, which generally means removing the final syllable of the infinitive, but with some specific details as follows:

Infinitive	Stem form	Examples
-Cre (where C is a consonant)	Remove -Cre	suivre > sui- connaître > connai- mettre > met-
-dre	As above, but d is preserved in writing.	perdre > perd-.
-Vre (where V is a vowel)	Remove -re	dire > di-
-Cir (where C is the characteristic consonant)	Remove -Cir	dormir > dor-
-Cir (where C is not the characteristic consonant)	Remove -ir	mourir > mour-
-Vir (where -ir isn't a syllable: i in the spelling represents part of a glide: oi [wa])	Remove -r	voir > voi- fuir > fui-

Note that in the case of -dre verbs, the preservation of the d in the stem is puraly a spelling complication, and the d is not pronounced in singular forms.

Another spelling complcation concerns n where this represents nasalisation on a vowel. For example, in peindre, the n isn't pronounced as a consonant¹ but is really part of the representation of the vowel ein [æ̃]. As such, it is preserved in the written form of the stem peind-.

As a general rule:

If the characteristic consonant occurs in the infinitive, it is not present (at least in the spoken form) in the singular forms and so can be considered not to be part of the stem.

The interaction between the vowel change and the consonant is a little more complex in the case of -enir verbs, and it is probably easiest to learn these explicitly. (See the full verb table of venir and full verb table of tenir.)

Singular forms

The singular present tense forms of irregular verbs are generally made by adding -s, -s, -t to the stem (for the je, tu and il forms respectively).
In the spoken language, the singular forms will sound the same.

In a small number of cases, the vowel change occurs in the singular forms (e.g. mourir > je meurs).

There are occasional spelling complications: -t is not written after -d (il perd) or -c (il vainc).

Plural forms

The plural forms are generally formed as follows:

Take the stem and apply any vowel change.
Add the characteristic consonant, if any.
Add -ons, -ez or (in writing) -ent.

Where the vowel change is from oi ([wa]), or in the case of u > eu, the vowel change distribution is slightly different: oi changes in the nous and vous forms; u > eu occurs just in the ils form (as well as in the singular).

Imperfect tense

As for virtually all verbs, the imperfect tense is formed as follows:

Remove -ons from the nous form and add the regular imperfect endings.

Future tense

The future tense is formed by adding the future tense endings to the future stem: either to the infinitive minus any final -e or, in the case of a few specific verbs, to its irregular future stem.

Conditional tense

The conditional, as for any verb, is based on the future tense forms but with the imperfect tense endings. See the page on the conditional for more information.

(Present) subjunctive

Irregular verbs don't generally have any special formation. As for virtually any verb:

The singular present subjunctive forms are the ils present tense form but with -e(s) instead of -ent.
The nous and vous forms are identical to the imperfect.
The ils subjunctive form is identically to the "normal" (indicative) present tense form.

This means that (both in written and spoken forms) the singular subjunctive forms are characterised by having the characteristic consonant and vowel change, whereas thes normally only occur in plural present tense forms.

Just a handful of irregular verbs have irregular subjunctive forms.

Notes:
1. In some accents of French, but not in what is generally regarded as a "standard French" accent, [æ̃] is pronounced (e.g. [ɛ~n] or [ɛ~ŋ]) with a nasal consonant at the end of the vowel.

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