初等幾何学における面（めん、英: face）は、立体図形の境界を成す二次元の図形を言う。
The basic building block of a battery. It is an electrochemical device consisting of an anode and a cathode in a common electrolyte kept apart with a separator. This assembly may be used in its own container as a single cell battery or be combined and interconnected with other cells in a container to form a multicelled battery.