an action, situation, or decision that has already happened and can be used as a reason why a similar action or decision should be performed or made

There are several precedents for promoting people who don't have formal qualifications. 提拔没有正式学历的人是有几个先例的。

Some politicians fear that agreeing to the concession would set a dangerous precedent. 一些政客担心同意让步会开创危险的先例。

the way that something has been done in the past that therefore shows that it is the correct way

Would it be breaking with precedent for the bride to make a speech? 新娘发表讲话是否有悖于惯例？

a decision about a particular legal case that makes it likely that other similar cases will be decided in the same way

The judgment on pension rights has established/set a precedent. 对养老金领取权的裁决成了一个判例。