French phrase
Savez-vous pourquoi ~ ?
Meaning
Do you know why ___?
When to use it
A polite way to ask about a reason. Common in everyday conversation and mildly non-intrusive.
Example dialogue
Savez-vous pourquoi il est parti si tôt ?
Do you know why he left so early?
Oui, il ne se sentait pas bien.
Yes, he wasn't feeling well.