未 + Verb
The adverb 未 (wèi) means 'not yet' or 'have not' and is used in formal or literary Chinese to negate a completed action. It functions similarly to 没有 but is more formal. It commonly appears in combinations like 尚未 (not yet) and 未来 (future, literally 'not yet come').
作业未完成的同学请留下来。
Zuòyè wèi wánchéng de tóngxué qǐng liú xiàlái.
Students who haven't finished their homework, please stay behind.
双方未能就价格达成一致。
Shuāngfāng wèi néng jiù jiàgé dáchéng yīzhì.
The two sides failed to reach an agreement on the price.
未经批准不得进入此区域。
Wèi jīng pīzhǔn bùdé jìnrù cǐ qūyù.
Entry to this area is not permitted without approval.