toughen：to become more strict，or to make something more strict.
tough 形容词指艰难的，强硬的，结尾➕en 变动词 加强
例：Chinese authorities have toughened their control of cryptocurrency trading. 政府加强了对虚拟货币交易的控制
仿：Chinese authorities have toughened their control of pyramid schemes.政府加强了对非法传销的控制
toughen 也经常用作 toughen up，例句中的 toughen 都可换成 toughen up。
toughen 后面➕政策（policy）、规章（rule）、惩罚（penalty/punishment）类的词
翻译：The government has toughened the restrictions and punishments on on-line car hailing services.
造句：National finance department has toughened the restrictions and punishment on the paycheck of celebrities.
