C'est vs Ce sont: agreement with predicate

French has a small piece of grammar that almost every native speaker is aware of, that almost every native speaker breaks every day, and that nevertheless turns up on every C1 exam paper: the choice between c'est and ce sont. The rule, on paper, is simple — singular predicate takes c'est, plural predicate takes ce sont. The reality, in the mouth, is that c'est has been quietly absorbing the plural for over a century, and the prescriptive ce sont now lives mostly in writing, formal speech, and the careful production of editors and teachers.

This page covers exactly when ce sont is required (formal register), when c'est is tolerated even before plurals (everyday speech), and the cases where c'est is mandatory regardless of what follows. The goal is for you to make a register-conscious choice rather than a guess.

The prescriptive rule

In standard written French, the verb être in the construction c'est / ce sont agrees in number with what follows it. Singular complement, singular verb. Plural complement, plural verb.

So far, so logical. The verb agrees with the noun phrase in the same way être agrees with any subject — except that the grammatical subject here is ce, a neutral demonstrative, and the agreement is being driven by the predicate noun rather than the subject. This is unusual. In most languages (and in most other French constructions), the verb agrees with the subject, not with what comes after the verb. Ce sont is the major exception.

What spoken French actually does

Now the reality. If you spend a day listening to native French — radio interviews, conversations, films — you will hear c'est mes parents, c'est des livres, c'est eux far more often than you will hear ce sont mes parents, ce sont des livres, ce sont eux. The shift is not a recent slang phenomenon. It has been documented in French grammars for over a hundred years, and c'est + plural is now the default in everyday speech.

In each of these the prescriptive form would be ce sont — and a careful editor would change them. But in conversation, on the radio, in films, in text messages, the c'est form is what comes out. Treating c'est + plural as an error in spoken French would mean correcting most of the country's population most of the time. It is not an error. It is a register feature.

Cases where c'est is mandatory regardless of plurality

There is one set of cases where c'est — not ce sont — is required even in the most formal register: the first and second person plural pronouns nous and vous. You do not say *ce sont nous; you say c'est nous. The same goes for vous.

This is non-negotiable across all registers. Even the most prescriptive grammar manuals accept c'est nous and c'est vous as the only correct forms. The reason is partly historical (the pronouns nous and vous have a special status as discourse participants rather than third-person referents) and partly phonetic (the sequence *ce sommes nous would clash with the verb form sommes not matching the third-person frame).

By contrast, the third-person plural pronouns eux and elles trigger the standard alternation:

Both are heard. The first is what you write. The second is what you say.

Where ce sont is genuinely required

In formal writing — published prose, journalism, academic writing, legal documents, exam essays — ce sont is expected before any plural noun phrase or third-person plural pronoun. Using c'est there is not a clever stylistic choice; it is treated as a careless error. If you are writing a dissertation for the baccalauréat, a cover letter for a job, or a university paper, use ce sont before plurals.

In journalism and broadcast French, ce sont is also the default. A news anchor saying c'est mes parents qui ont décidé would sound out of place — not wrong, exactly, but oddly informal. Ce sont mes parents qui ont décidé is what is expected.

The case of c'est + numerical phrases

A subtle area: when the predicate is a numerical phrase like deux euros, trois ans, cinq personnes, the spoken form is overwhelmingly c'est, even in relatively careful registers.

For prices, distances, durations, and quantities given as raw figures, c'est is normal even in careful speech. The reason is that the numerical phrase is functioning more like a measurement than a count of distinct entities — and the verb tracks that semantic singularity.

When the numerical phrase shifts to counting distinct individuals, ce sont becomes more natural in formal register:

Tense variation: c'était vs c'étaient, ce sera vs ce seront

The same alternation operates in other tenses, with the same register split. The imperfect c'était / c'étaient (the elision before a vowel is obligatory — you never see ce étaient spelled out), the future ce sera / ce seront, and the conditional ce serait / ce seraient all follow the pattern: prescriptive plural agreement, spoken singular tendency.

In compound tenses, the pattern continues — ç'a été / ç'ont été split the same way, though the compound forms are themselves rare in everyday speech. The ç' spelling preserves the c + cedilla logic when the consonant lands before a.

Comparison with English speakers' expectations

English does not have this problem because it is invariably singular and they is invariably plural. It's the kids and They're the kids are not equivalent — the second is awkward in English in a way it is not in French. French c'est corresponds roughly to it's and that's; ce sont corresponds roughly to those are and they are (when introducing). English speakers learning French tend to under-use ce sont because their native instinct says it matches all numbers. The corrective: when you are presenting or identifying a plural entity in formal writing, switch the verb to sont.

A second English-speaker pattern: avoiding the issue entirely with they are equivalents. Ils sont mes parents is grammatically possible but means something different — it is a descriptive predication (they are my parents, identifying who they are) rather than a presentational identification (these are my parents, pointing them out). The two structures are not interchangeable, and the c'est / ce sont construction is the right tool for presentation.

Common Mistakes

Key Takeaways

The choice between c'est and ce sont is fundamentally a register choice, not a grammar choice. The prescriptive rule (ce sont before plural) is real and required in writing. The descriptive reality (c'est before plural) is dominant in speech. Mastering this means knowing which register you are operating in. For formal writing and exam contexts, use ce sont before plural noun phrases and eux / elles. For everyday speech, c'est is the natural choice. With nous and vous, always c'est. With first-person singular moi, always c'est. With prices and measurements, c'est. Everywhere else, let register guide you.