Iff
[计] 如果仅仅, 当且仅当, \等价\
🗣️ 情景例句
till you get to the end of the fence.
到栅栏的尽头。
Who are those people?
那些人是谁？
Please do. We 're desperate for the material.
麻烦你了，我们非常需要这些材料。