/ˈɒpʃənl ||; ˈɑpʃənḷ/adj
that you can choose or not choose 可选择的;非强制性的:
an optional subject at school学校里的选修科目 [OPP] compulsory or obligatory 反义词为compulsory或obligatory
optional/ˋɑpʃənḷ; ˈɒpʃ$nəl/adj if something is optional, it is available but you do not have to choose it [ compulsory ] 可选择的﹐非强制的: The sunroof is optional. 车顶天窗是可选配置。
optionaladjectiveIf something is optional, you can choose it or not choose it: All students must learn English, but German is optional.oppositecompulsory