family什么时候变为families

family的用法,什么时候写成families? 详细解释下family什么时候可数,什么时候不可数,families是指什么 family families区别 family与families的用法 three family和three families的区别 The two are at home now.family or families family 意为家人时复数需要变成families吗? family做家庭成员来讲是复数,形式是不是为families? 三个家庭成员是three family还是three families? All happy families are like one another; each unhappy family 要表示两个家人,是two family还是two families family什么时候用可数什么时候不可数