表泛指的复数名词,通常用 ones.
表泛指的单数名词,通常用 one.
注：若 one 前没有形容词的修饰,则其前不能有不定冠词
Green apples often taste better than red ones.青苹果往往比红苹果好吃
I lost my old camera; this is a new one.我的旧相机丢了,这是一架新的.
This pen doesn’t work.I must buy another one.这支钢笔坏了,我要另买一支了