电路中的一个参考点，该点电位作为<em>标称的</em>零电位，其它所有电位均相对于该点而定。经常，但并非总是，将该点直接连接到地。作为动词，指连接到地线上的过程，也称作接地。
A point considered to be at nominal zero potential and to which all other potentials in the circuit are referred, often, but not always, connected to the actual surface of the earth; as a verb to connect to a ground. Also called earth.
