Iff
[计] 如果仅仅, 当且仅当, \等价\
🗣️ 情景例句
She is at the top of her class.
她在班里名列前茅。
Do not to others what you do not wish them to do to you.
己所不欲，勿施于人。
He came out of the library, a large book under his arm.
他夹着本厚书，走出了图书馆。