How do you say know why speak In french?

There are a few ways to say "know why speak" in French, depending on the context and nuance you want to convey. Here are some options:

1. "Tu sais pourquoi je parle?" (Formal/Informal) - This is the most direct translation and means "Do you know why I'm speaking?"

2. "Tu comprends pourquoi je parle?" (Formal/Informal) - This means "Do you understand why I'm speaking?"

3. "Tu sais pourquoi je te parle?" (Informal) - This means "Do you know why I'm talking to you?"

4. "Tu as compris pourquoi je parle?" (Formal/Informal) - This means "Have you understood why I'm speaking?"

5. "Tu sais pourquoi je dis ça?" (Informal) - This means "Do you know why I'm saying this?"

6. "Tu comprends pourquoi je fais ça?" (Informal) - This means "Do you understand why I'm doing this?"

The best way to choose the right phrase depends on the context of the conversation. For example, if you're trying to explain something, "Tu comprends pourquoi je parle?" might be the best option. If you're asking someone why they're acting a certain way, "Tu sais pourquoi tu fais ça?" might be more appropriate.

Remember that French has a formal and informal register. You would use "tu" with close friends and family and "vous" with strangers or people you want to be polite to.