Learn Hardcore French: C'est Marie qui décide où nous allons dîner. - It is Marie who decides where we are going to have dinner.

It’s a cleft sentence used to put focus on the element inside it. Here, it highlights that it’s specifically Marie who makes the decision. The non-cleft version is simply: Marie décide où nous allons dîner. The meaning is the same, but the cleft adds emphasis or contrast (often answering Who decides?).

Why is it qui and not que after Marie?

Because the focused element (Marie) is the subject of the verb that follows. Use:

qui when the focused word is the subject of the following verb: C’est Marie qui décide.
que when it’s the direct object: C’est Marie que j’appelle.

Could we drop the cleft and just say Marie décide où nous allons dîner?

Yes. That’s the neutral, un-emphasized version. The cleft (C’est Marie qui…) is preferred when you want to stress that it’s Marie (and not someone else).

Why C’est and not Il est?

Use C’est to identify or point to a specific person or thing with a noun or name: C’est Marie.
Il est is used with adjectives or professions, or when the noun is not specified: Il est tard, Il est professeur. With a proper name, use C’est.

Why is there no inversion or est-ce que in où nous allons dîner?

Because this is an indirect question (embedded after décide). In indirect questions, French keeps normal subject–verb order: où nous allons dîner, not où allons-nous dîner and not où est-ce que nous allons dîner.

What is nous allons dîner grammatically, and could we use nous dînerons instead?

Nous allons dîner is the near future (futur proche), common in speech for planned or imminent events. You can use the simple future nous dînerons too; it’s slightly more formal or more distant. Both are correct here.

Could we use the present and say où nous dînons?

You can, but it shifts the nuance. Où nous dînons can sound like a standing arrangement or a present-time decision. For a plan about the near future (tonight, for example), où nous allons dîner is the most natural.

Does décider need de here?

Not in this structure. Patterns to remember:

décider de + infinitive: Marie décide de partir.
décider que + indicatif: Marie décide que nous partons demain.
décider + mot interrogatif (où, quand, qui…) + proposition: Marie décide où nous allons dîner.

Can we say C’est Marie qui décide où aller dîner? What changes?

Yes. Où aller dîner uses an infinitive clause. It’s a bit more compact and leaves the subject of aller implicit, understood from context (here, us). If you want to be explicit, keep où nous allons dîner.

How does verb agreement work after qui in this pattern?

The verb after qui agrees with the antecedent of qui:

C’est moi qui décide.
C’est toi qui décides.
C’est nous qui décidons.
C’est vous qui décidez. Here, with Marie, it’s third-person singular: qui décide.

Do we need the subjunctive anywhere?

No. After décider que, French normally uses the indicative (it’s a decision, not doubt/feeling). With où introducing an indirect question, you also use the indicative: où nous allons dîner.

What exactly is où doing here?

It introduces an indirect question (interrogative subordinate clause) meaning where. It’s not a direct question, so there’s no inversion or est-ce que. It links décide to the content of the decision.

Any spelling/accent points to watch?

où (where) has a grave accent; ou without an accent means or.
décide has an acute accent on é.
dîner traditionally has a circumflex on i; the spelling without it (diner) is also accepted in the 1990 reforms, but dîner is still very common.

Could we replace nous with on for a more colloquial tone?

Yes: C’est Marie qui décide où on va dîner. In everyday speech, on often stands in for nous.

How would you make this negative?

Standard: Ce n’est pas Marie qui décide où nous allons dîner.
Colloquial speech often drops the ne: C’est pas Marie qui décide…

Any quick pronunciation tips?

C’est: [sɛ]
Marie: [maʁi]
qui: [ki]
décide: [desid]
Liaison in nous allons: [nu.za.lɔ̃]
où: [u]
dîner: [dine]
Say it smoothly as: [sɛ maʁi ki desid u nu.za.lɔ̃ dine].