discretionary
/dɪsˈkɹɛʃəˌnɛɹi/ 形容词 C1中文： 自由裁量的、任意的
- Available at one's discretion; able to be used as one chooses; left to or regulated by one's own discretion or judgment. · discretionary income· discretionary powers
来自图书馆
The United Kingdom occupies a middle ground, where service charges are sometimes included on the bill, but additional tipping remains entirely discretionary.
在真实文章中学习discretionary
注册免费账号后，在图书馆中把鼠标悬停在任何单词上即可看到意思，还能听朗读、收藏单词并按你的记忆安排复习，看到每本书你已经认识多少。