Using "si" instead of "oui" to disagree with a negative question or statement in French

In most cases, we use oui (yes) and non (no) in French the same way as in English.

However, if someone asks you a negative question or makes a negative statement and you want to disagree with it (i.e. answer in the positive) then use si instead of oui.

Learn when to use "Si" or "Oui" in French 

Agreeing...

Est-ce que tu parles français? Oui, je parle français.Do you speak French? Yes, I speak French.

Disagreeing...

Tu ne t'amuses pas? - Si, je m'amuse.Aren't you having a good time? - Yes, I am.

Il n'est pas gentil. - Si, il est gentil.He's not nice. - Yes, he is. 

Bref, ce n'est pas important... - Si, c'est important !Anyway, it's not important... - Yes, it is!

Tu n'as pas une clope? - Si.Don't you have a smoke? - Yes I do.

Summary:

- Use Oui to answer "yes" to positive questions/statements

- Use Si to answer "yes" to negative questions/statements 

Note that non is always the same whether you are agreeing or disagreeing:

Est-ce que tu parles français? Non, je ne parle pas français.Do you speak French? No, I don't speak French.

Tu ne parles pas français?  - Non, je ne parle pas français.Don't you speak French? - No, I don't speak French.

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Learn more about these related French grammar topics

Examples and resources

Il n'est pas gentil. - Si, il est gentil.He's not nice. - Yes, he is. 
Bref, ce n'est pas important... - Si, c'est important !Anyway, it's not important... - Yes, it is!
Tu ne parles pas français?  - Non, je ne parle pas français.Don't you speak French? - No, I don't speak French.
Tu ne parles pas français?  - Si! Je parle français.Don't you speak French? - Yes! I do speak French.
Tu ne t'amuses pas? - Si, je m'amuse.Aren't you having a good time? - Yes, I am.
Tu n'as pas une clope? - Si.Don't you have a smoke? - Yes I do.
Est-ce que tu parles français? Non, je ne parle pas français.Do you speak French? No, I don't speak French.

Attention


Est-ce que tu parles français? Oui, je parle français.Do you speak French? Yes, I speak French.
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