Faculative
a. 允许的, 任意的, 兼性的, 偶发的
🗣️ 情景例句
It was a gradual process, involving many factors.
这是个渐进的过程，涉及到方方面面。
Nothing must be done hastily but killing of fleas.
除非消灭跳蚤，做事不必急躁。
You just don't consider anyone but yourself.
你除了自己外从不为别人考虑。