Être: the most irregular verb in French.

Présent — six words, no pattern

Most irregular verbs at least keep a recognisable stem. Être does not: suis, es, est, sommes, êtes, sont share almost nothing. This is a memorisation job, and it is worth doing on day one.

What être does that English be does not

Two habits catch English speakers early, and both are quick to fix.

The second is the c’est / il est split. Use c’est before a noun (c’est un ami, c’est ma sœur) and il / elle est before a bare adjective or a job (il est grand, elle est avocate). If there is an article in front, it wants c’est.

And one useful construction: être en train de + verb is how French says “to be in the middle of doing” — je suis en train de manger, “I’m eating right now”. French has no separate continuous tense, so this is what fills the gap when you need to stress that something is happening at this moment.

Passé composé — and the verbs that borrow it

A pleasing wrinkle first: être builds its own past with avoir, not with itself. J’ai été — “I have been”.

The bigger story is what être does for other verbs. A short list of movement-and-change verbs takes être as their helper instead of avoir — and when they do, the participle agrees with the subject the way an adjective would.

The verbs that take it are the ones about coming, going and changing state: aller, venir, arriver, partir, entrer, sortir, monter, descendre, rester, tomber, naître, mourir, retourner, passer — plus every reflexive verb, without exception.

Imparfait — the one verb that breaks the rule

Every other verb in French builds its imparfait from its own nous form: drop the -ons, add the endings. Être would give somm-, which is not what happens. The stem is ét-, and it is the single exception in the entire language.

It is also one of the most useful tenses you will learn, because describing how things were is most of what talking about the past involves: c’était — “it was” — is a phrase you will say every day.

Futur and conditionnel — the ser- stem

Another stem with no visible relationship to the infinitive: ser-. It gives both the futur and, with the imparfait endings, the conditionnel.

Conditionnel — would be

Ce serait bien — “that would be nice” — is worth learning as a block. The conditionnel is the register of suggestions and soft opinions, and French uses it far more readily than English uses “would”.

Subjonctif — the one you will meet most

If you learn one subjunctive, learn this one. Il faut que tu sois là — “you need to be there” — and je suis content que tu sois là are the kind of sentences the subjunctive exists for, and être turns up in them constantly.

Impératif and plus-que-parfait

Like avoir, the imperative is lifted from the subjunctive. Sois sage — “be good” — is what French parents say roughly four hundred times a day.

Plus-que-parfait

The imparfait of avoir plus the participle: j’avais été, “I had been”. Used for a state that was already over before the moment you are talking about.