唯一 (wéi yī): only, sole

He is my only older brother; whenever I run into difficulties, I always go to him first for help.

This exam is the only chance to get my diploma, so I study until late every day.

In the desert, water is the only thing that can save lives, so we must use it sparingly.

This small bookstore is the only place in town that sells Chinese books; many elderly people like to come here to read.

Her only wish is that her family be healthy and safe; nothing else matters.

The police confirmed that the only clue was the fingerprint left at the scene, so they began investigating.