the fact of not voting in favour of or against someone or something

There were high levels of abstention (from voting) in the last elections. 上几次选举中都有很多人放弃了投票权。

There were ten votes in favour, six against, and three abstentions. 10票赞成，6票反对，3票弃权。

not doing something, such as drinking alcohol or having sex

Abstention from alcohol is essential while you are taking this medication. 服用这种药物期间，一定要戒酒。