Le Présent: Boire et Croire

Boire ("to drink") and croire ("to believe") are two high-frequency irregular verbs that, despite their similar appearance and shared -oire ending, differ in interesting ways. Boire has three stems (boi-, buv-, boiv-) with a dramatic vowel shift from /wa/ to /y/ to /wa/ across the paradigm. Croire has only two stems (croi-, croy-) and stays closer to its base sound. Together they teach the -oire family pattern, the partitive article system that follows boire, and one of the most productive subjunctive triggers in the language: the rule that croire que takes the indicative when affirmed but switches to the subjunctive when negated or questioned.

This page covers both paradigms with phonetic detail, walks through the major uses, addresses the boire + partitive constraint that English speakers consistently miss, and unpacks the subjunctive-toggle behavior of croire que that has no equivalent in English.

The full paradigm — boire

Past participle: bu /by/. Auxiliary: avoir. J'ai bu — "I drank."

The full paradigm — croire

Past participle: cru /kʁy/. Auxiliary: avoir. J'ai cru — "I believed."

The stem alternations — three vs two

This is where the two verbs diverge. Compare:

Boire uses three stems with a striking vowel shift:

• /wa/ in the singular (je bois /bwa/) — diphthong
• /y/ in nous/vous (nous buvons /byvɔ̃/) — front rounded vowel, the "u" of tu
• /wa/ again in the 3pl (ils boivent /bwav/) — back to the diphthong, plus an audible /v/

This is unusually dramatic — the vowel actually changes quality from /wa/ to /y/ and back, not just a stem-final consonant added or dropped. This is a vestige of Old French phonology that fossilized in this small handful of verbs.

Croire uses only two stems, and the change is gentler:

• /kʁwa/ in the singular and 3pl (je crois, ils croient — both /kʁwa/)
• /kʁwaj/ in nous/vous (nous croyons /kʁwajɔ̃/) — adds a /j/ glide between the diphthong and the vowel-initial ending

The 3pl ils croient is pronounced identically to the singular /kʁwa/ — there is no audible -v- or -y- in the 3pl. This is one of those cases where French gives you no audible singular/plural distinction at all; you must rely on the subject pronoun (il /il/ vs ils /il/ — themselves homophones, distinguished only by spelling) or a following liaison cue.

Use 1: Boire — drinking, with the partitive

The fundamental thing about boire is that it almost always takes a partitive article (du, de la, des) before the thing being drunk. This is because what you drink is typically an unspecified quantity of a substance — "some water," "some wine," "some coffee."

After negation, the partitive collapses to de (or d' before a vowel): je ne bois pas *de vin (not *du vin).

When you specify a definite amount or a particular drink, the partitive disappears and a different article takes over:

• Definite ("the wine" — a specific one): je bois *le vin que tu as apporté.*
• A specific glass / cup: je bois *un café* — "I'm having a coffee" (one cup).
• A whole quantity: je bois *une bière* — "I'm having a beer."

For the full treatment, see Partitive Articles.

Use 2: Boire — idioms and figurative uses

A handful of high-frequency expressions:

Use 3: Croire — belief and opinion

Croire covers both religious / philosophical belief and everyday opinion. The construction shifts depending on what you believe:

Croire que + clause = "to think / believe that":

Croire à + noun = "to believe in / believe the existence of" (used for abstract concepts, fairy-tale figures, ideals):

Croire en + noun = "to believe in / have faith in" (used for God, persons, principles — implies trust):

The distinction between croire à and croire en is delicate. Roughly: croire à is "to believe in the existence/reality of" (you can croire à un fantôme — believe ghosts exist), while croire en is "to have faith in / put trust in" (croire en quelqu'un — believe in someone's ability or worth). With God, both are possible — croire en Dieu is the more idiomatic for personal faith; croire à Dieu is rarer and shades into "believe God exists."

Use 4: The subjunctive trigger — croire que

This is one of the most productive subjunctive triggers in French and a place where English has no equivalent. The rule:

• Croire que + indicative when the belief is affirmed: je crois qu'il *est là.*
• Ne pas croire que / croire que (in question) + subjunctive when the belief is denied or doubted: je ne crois pas qu'il *soit là. / Crois-tu qu'il soit là ?*

The logic: when you affirm a belief, the embedded clause is presented as a fact (or near-fact) in your model of the world — the indicative marks reality. When you deny or question the belief, the embedded clause is presented as uncertain or false — the subjunctive marks irrealis (doubt, possibility, non-fact).

In informal speech, the indicative sometimes survives in questions ("Tu crois qu'il vient ?" with indicative vient) — this is widespread but technically the formal grammar prefers the subjunctive in questions too. In careful writing, always use the subjunctive after ne pas croire que and after questions with croire.

The same toggle applies to penser que (think that) and espérer que (hope that — though this is more complex). But not to verbs of perception (je vois, je sais), which take the indicative even when negated. For the full treatment, see Subjunctive: Doubt and Uncertainty.

Use 5: Croire — fixed expressions

A few high-frequency expressions:

The reflexive se croire + adjective is a useful and slightly disparaging construction: it expresses that someone overestimates themselves (il se croit malin — "he thinks he's clever"). The construction on se croirait + place/time describes a strong impression of being somewhere or in some era.

A side-by-side reference

Common Mistakes

Mistake 1: Forgetting the partitive after boire.

Mistake 2: Using du / de la after a negation.

Mistake 3: Indicative after ne pas croire que.

Mistake 4: Confusing croire à and croire en.

Mistake 5: Wrong stem in nous/vous of boire.

The /wa/ → /y/ stem shift in boire is dramatic and easily forgotten. Nous buvons, not nous boivons (which doesn't exist) or nous boivvons (also wrong).

Mistake 6: Wrong past participle.

(Boi is not a French word. Bu is the irregular past participle.)

Key takeaways

Boire and croire are best learned together as a pair. They share the -oire family ending and a general orientation around states (drinking, believing) rather than actions, but their internal structure differs.

Three points to internalize:

1. Three stems for boire, two for croire. Boire alternates among /bwa/, /byv/, /bwav/ — a dramatic vowel shift that surprises learners. Croire alternates only between /kʁwa/ and /kʁwaj/ — gentler. Memorize the full paradigms; the patterns are not predictable from the infinitives alone.
2. Boire requires the partitive. Je bois *du café, not *je bois café. After negation it collapses to de: je ne bois pas *de café*. This is a place where French and English diverge sharply — English has no partitive system, so learners must consciously add the article.
3. Croire que is a subjunctive trigger when negated or questioned. Je crois qu'il est là (indicative) but je ne crois pas qu'il *soit là (subjunctive). The toggle is productive — same logic applies to *penser que and other verbs of opinion. This is one of the most consequential subjunctive triggers in spoken French.

Once boire and croire are solid, study Voir for the -oir family more broadly, and the doubt/uncertainty subjunctive triggers for the wider system croire que belongs to.