dent+ ist→dentist n.牙科医生

例句：

The dentist told the boy not to eat too many sweets.

牙医告诫这男孩不要吃太多糖果。

11.-ster：

young+ ster→youngster n.年轻人

例句：

That youngster works with a will.

这小伙子干活有股傻劲儿。

gang+ ster→gangster n.歹徒

例句：

The police are hard on the track of the gangster.

警察正在追踪那名匪徒。