optionalKK [ˋɑpʃənəl] /ˈɑpʃənəl/發音形容詞1可選擇的、非強制的、自由決定的Attendance at the morning meeting is optional for part-time staff.兼職員工可自行決定是否出席晨會。2選修的教育She took two optional courses in film history this semester.她這學期選修了兩門電影史的課。3選配的、額外加購的Leather seats and a sunroof are optional on this model.這款車的真皮座椅和天窗屬於選配。