* "How so?" This is the most common translation and is used when you are asking for clarification or explanation.
* "What do you mean?" This is another common translation and is used to express confusion or disbelief.
* "Really?" This is used to express surprise or disbelief.
* "How is that?" This is less common but can be used in situations where you are asking someone to elaborate on how something is possible.
Example:
* "Je suis fatigué." "Comment ça?" (I am tired. How so?)
* "J'ai gagné à la loterie." "Comment ça?" (I won the lottery. What do you mean?)
The specific translation of "comment ça" will depend on the context of the conversation and the tone of the speaker.