(idiomatic) A piece of cake; an extremely simple thing, something trivial, a cinch, easy as pie.

朝飯前: A piece of cake; an extremely simple thing.

(telephony) a common Japanese telephone greeting: hello; used when answering the telephone / used to confirm that the person being addressed is listening, or to confirm if anyone is listening

put away

足: foot / 脚: leg

necessity (quality or state of being necessary, unavoidable, or absolutely requisite)

unnecessary

needlessness

necessary evil

operating room, operating theatre