sth是something的缩写,意为“某事/物”.常用于英语句型或短语记忆.

something

pron.某事;某物;想来重要(或值得注意)的事物;(表示不确切的描述或数量)大致，左右

adv.(与形容词连用)很，非常

It's important to try and make something of your life.

在一生中有所成就是很重要的。

First try to do something that is within your scope.

你先试着做一件自己力所能及的事。

I'm sure she's keeping something back from us.

我肯定她有什么事瞒着我们。