time表示时间,为不可数名词,不能加s;表示次数,倍数,为可数名词,复数形式要加s.
fish表示鱼肉,为不可数名词,不能加s;表示鱼类,为可数名词,复数形式要加s.
例:I have been to Beijing three times.This tree is three times longer than that one.
鱼[M][C]; 鱼类[C] They have a large collection of fishes.他们收集了大量的各种鱼类.Fish are cold-blooded.鱼是冷血动物.鱼肉[U] We'll have fish for dinner.我们晚餐吃鱼.