ou vs où

Summary

ou (no accent) is the conjunction "or" offering a choice (thé ou café); où (grave accent) means "where" — a place — and, after a time word, "when" (où vas-tu ?, le jour où). Decision rule: if you can replace it with "or" (ou bien), write ou; if it really means where/when, write où.

Explanation

These two words are homophones but do opposite jobs in a sentence. Ou without an accent is the coordinating conjunction "or." It links two alternatives and offers a choice: thé ou café ?, tu viens ou tu restes ?, c'est blanc ou noir. Anywhere you are presenting options, the accent-free ou is what you want.

Où with a grave accent is about place. As a question word it means "where": où vas-tu ?, où est la gare ? As a relative it links a clause to a place already mentioned: la ville où je suis né, le pays où ils habitent. French also extends this où to time after a noun referring to a moment, where English would say "when": le jour où il est parti, l'année où nous nous sommes rencontrés.

The decision rule is a quick substitution. Mentally replace the word with "or" — or, more reliably, with the French ou bien ("or rather / or else"). If the sentence still makes sense, it is the conjunction and you write ou with no accent: café ou bien thé. If the substitution is nonsense and the word is actually asking or pointing to where (or when), you write où with the accent.

Watch the test work. In tu prends le bus ou le train ? you can say ou bien le train, so it is ou (no accent). In où es-tu ? you cannot say "or bien es-tu," and the sense is clearly "where," so it is où. The same sorts la salle où on mange (a place → où) from sucre ou sel (a choice → ou).

A note on the accent and on the time use. The grave accent on où is not optional or decorative — it is the only thing distinguishing the two words in writing, so leaving it off turns "where" into "or." And the "when" sense of où only appears after a noun of time (le moment où, la semaine où); to ask "when?" as a standalone question you use quand, not où.

Summary: ou = a choice between options (replaceable by "or" / ou bien); où = a place, or a moment after a time noun ("where / when"). One substitution test settles it: if "or" fits, drop the accent; if the meaning is where/when, keep the accent on où.

Examples

Tu préfères le thé ou le café ? — Do you prefer tea or coffee? (ou: a choice; you could say le thé ou bien le café.)

Où est la gare, s'il vous plaît ? — Where is the station, please? (où: a place; "or bien" makes no sense here.)

On part aujourd'hui ou demain ? — Are we leaving today or tomorrow? (ou: choice between two options (today / tomorrow).)

C'est la maison où je suis né. — This is the house where I was born. (où: relative referring to a place (the house).)

Je me souviens du jour où nous nous sommes rencontrés. — I remember the day when we met. (où after a time noun (le jour) means "when" in English.)

Common mistakes

Related rules

• Relative pronouns (qui / que / dont / où)
• Question formation: intonation / est-ce que / inversion
• a vs à