that you can choose to do or have if you want to 可选择的;选修的 Certain courses are compulsory; others are optional. 有些课程是必修的,其他是选修的。 This model comes with a number of optional extras (= things you can choose to have but which you will have to pay extra for). 这一型号有一系列可供选择的附件,价格另计。 These features can be offered as an optional part of the package. 这些功能可以作为软件包的可选部分提供。
Oxford Collocations Dictionaryverbs- be
- make something
- entirely
- purely