英英释义：to become more strict, or to make something more strict
我们熟悉“tough”的意思是“艰难的” “（政策或行动）强硬的”，和很多形容词一样，它可以通过添加词缀变成动词 toughen，表示“加强”。
当我们想表达“make something more strict”的时候，就可以用更简洁的 toughen 来表示。比如，中国已经加强了对虚拟货币交易的控制：
Chinese authorities have toughened their control of cryptocurrency trading.
政府已经出台了新政策，加强电动车使用的规定：
The government has issued new policies to toughen the rules about using electric scooters.
toughen 也经常用作 toughen up，上面例句中的 toughen 都可以换成 toughen up。比如我们想说，新法规加强了对酒驾者的处罚和限制，就可以说成：
The new law toughens up penalties and restrictions for DUI offenders. （DUI 是 Driving under the influence 的缩写，就是我们常说的“酒驾”）
我们可以发现，toughen 后面常接有关政策（policy）、规章（rule）、惩罚（penalty/punishment）的名词。
最新一期的《经济学人》封面文章中也出现了 toughen：
Mr Trump and his administration have got three things right. The first is that America needs to be strong. It has toughened the rules on takeovers, to give more right to national security.
