Optional

['ɒpʃ(ə)n(ə)l] or ['ɑpʃənl]

解释:

(adj.) possible but not necessary; left to personal choice .

柏妮丝手打--From WordNet

解释:

(a.) Involving an option; depending on the exercise of an option; left to one's discretion or choice; not compulsory; as, optional studies; it is optional with you to go or stay.

(n.) See Elective, n.

整理:诺拉

同义词及近义词：

a. Discretional, elective.

编辑:尼特