optional
01
可选的, 非强制的
available or possible to choose but not required or forced
例子
Attendance at the seminar is optional; students can attend if they are interested in the topic.
研讨会的出席是可选的；如果学生对主题感兴趣，可以参加。
Optional
01
可选的, 非强制性的
something that is not required or mandatory, especially in an academic setting
例子
At the conference, attendees can select from a menu of workshops, with each workshop being an optional.
在会议上，与会者可以从一系列研讨会中选择，每个研讨会都是可选的。
词汇树
optionally
optional
option
opt
