DICT.TW Dictionary Taiwan

 op·tion·al /ˈɑpʃnəl, ʃənḷ/
 (a.)可選擇的,隨意的

 optional
 可選擇的

 optional
 任選 選項

 Op·tion·al a. Involving an option; depending on the exercise of an option; left to one's discretion or choice; allowed but not compulsory; as, optional studies; it is optional with you to go or stay. -- n. See Elective, n.
    If to the former the movement was not optional, it was the same that the latter chose when it was optional.   --Palfrey.
    Original writs are either optional or peremptory.   --Blackstone.
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 optional
      adj : possible but not necessary; left to personal choice [ant: obligatory]