tooth复数为teeth，为不规则变化，其意思是牙齿、齿状部分，例如to clean your teeth刷牙、the teeth on a saw锯齿等。其常见词组搭配有tooth decay龋病、tooth enamel牙釉质、lose a tooth掉牙、pull a tooth拔牙、cut a tooth长出新牙等。

例句：1、The front cog has 44 teeth.

前齿轮有44个齿。

2、I need to have two teeth filled.

我有两颗牙要补。

3、A high proportion of five-year-olds have teeth in poor condition.

五岁儿童牙齿不健康的比例高。

4、He laughed,revealing a line of white teeth.

他笑了起来，露出一排洁白的牙齿。

5、Dentists advise you to have your teeth checked every six months.

牙医建议大家每六个月检查一次牙齿。