The dormir verb pattern

A few common verbs of French have infinitives ending in -ir but have "short" forms in which the -i- of the infinitive isn't generally included in the other (conjugated) verb forms. This differs from the "regular -ir" pattern of verbs such as finir. So while finir has je finis etc, dormir has je dors etc.

Verbs of the dormir type have a characteristic consonant before the -ir. This consonant appears in all forms except the present tense singular forms. Unlike verbs of the so-called regular -re conjugation, the characteristic consonant is not included in the spelling of these singular forms either.

Which verbs?

The following closed list of verbs follow the dormir pattern (you can click on a verb to see its full conjugation):

dormir to sleep
mentir to lie, tell a lie
partir to leave
sentir to feel, smell
servir to serve
sortir to leave, go/come out
Their compounds: consentir, pressentir, ressentir, démentir, départir, repartir, ressortir¹, endormir, rendormir, desservir, resservir.

1. In some uses, ressortir follows the regular finir pattern.

Forms

The key to forming these verbs is to remember:

The stem is the infinitive minus -Cir, where C is the characteristic consonant. So dormir has the stem dor-.
The characteristic consonant then re-appears in all forms except the present tense singular forms.
The past participle ends in -i (with the characteristic consonant present, e.g. dormir > dormi).

Otherwise, these verbs are formed using general principles that basically apply to any French verb.

Present tense

The normal endings -s, -s, -t, -ons, -ez, -ent are added (these are generally the endings for any French verb except regular -er verbs); the characteristic consonant is inserted in the plural forms. This gives:

Verb (infinitive)	Person	Stem	Consonant	Ending	Form
dormir	je tu il/elle nous vous ils/elles	dor-	- - - -m- -m- -m-	-s -s -t -ons -ez -ent	je dors tu dors il dort nous dormons vous dormez ils dorment
servir	je tu il/elle nous vous ils/elles	ser-	- - - -v- -v- -v-	-s -s -t -ons -ez -ent	je sers tu sers il sert nous servons vous servez ils servent
sortir	je tu il/elle nous vous ils/elles	sor-	- - - -t- -t- -t-	-s -s -t -ons -ez -ent	je sors tu sors il sort nous sortons vous sortez ils sortent

Note that, as for most French verbs, all of the singular forms are pronounced the same.

Past participle

As mentioned, the past participle of these verbs ends in the characteristic consonant plus -i (effectively, remove -r from the infinitive). Hence perfect tense forms such as j'ai dormi, je suis sorti, j'ai servi.

Other tenses

Other tenses are formed as for any other verb:

The imperfect takes the stem dorm-, sort- of the nous present tense form, including the characgeristic consonant. This gives forms je dormais, je sortais etc.
The future tense is formed on the infinitive, giving je dormirai, je sortirai etc.
The conditional is the future but with imperfect endings, giving je dormirais etc.
The subjunctive takes the stem of the ils present tense form (i.e. it includes the characteristic consonant, dorm-, sort-) and adds the usual subjunctive endings, giving je dorme, je sorte etc.
The past historic is has endings with the -i- vowel like the past participle: il dormit, il sortit etc.

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