backward/backwards

backward /ˈbækwəd/ adj. 1.向后的，倒的(［反］forward): a backward glance 向后看一下；the backward journey 回来的旅途； the backward flow of the tide 潮水回流 2.落后，差(［同］behindhand;［反］advanced)：a backward pupil 迟钝的学生；a backward country in civilization 文化落后的国家；be intellectually backward 智力差

backwards /ˈbækwədz/ adv. (AmE.亦作 backward)向后，朝反方向，倒着：He looked backwards. 他向后看。count backwards from 10 to 1 从10到1倒着数  backwards and forwards 来回地： This train goes backwards and forwards between the two towns 这列火车在两个城镇间来回运行。