General understanding:
* "Pardon?" - This is the most common and polite way to ask someone to repeat themselves. It's similar to "Excuse me?" in English.
* "Excusez-moi?" - This is also a polite way to ask someone to repeat themselves, but it's slightly more formal than "Pardon?".
* "Je n'ai pas compris." - This literally means "I didn't understand," and is a more direct way of asking someone to repeat themselves.
To ask for clarification:
* "Pouvez-vous répéter?" - This means "Can you repeat that?" and is a more formal way of asking for clarification.
* "Qu'est-ce que vous avez dit?" - This means "What did you say?" and is a more direct way of asking for clarification.
To express surprise or disbelief:
* "Quoi?" - This is a more casual way to say "What?" and can be used to express surprise or disbelief.
* "Ah bon?" - This means "Really?" and can be used to express surprise or skepticism.
The best way to say "come again" in French depends on the specific situation and your level of formality.