noun
Honorific noun used to politely refer to the trouble or effort one causes someone else. Often used in set phrases like お手数ですが (I'm sorry to trouble you, but...) or お手数をおかけします (I apologize for the inconvenience).
See also: 手数
お手数ですが、もう一度メールを送っていただけますか。
I'm sorry to trouble you, but could you send the email once more?
お手数をおかけして申し訳ございません。
I apologize for causing you trouble.
手数 is the non-honorific form meaning 'trouble' or 'effort'; お手数 adds the honorific prefix お to show respect toward the person whose effort is involved.
Honorific prefix お + 手数 (てすう, 'trouble, effort'). The reading おてかず is a less common variant.