未

例句：

1. 1.We haven't seen each other for a long time.
   我们很久没有见面了。
2. 2. The book is not available in this store.
   这本书在这家店里买不到。
3. 3.You can't say "no" to me, I'm your boss.
   你不能拒绝我，我是你的老板。