definitive

No one has come up with a definitive answer as to why this should be so.

至于为什么该这样，还没有人给出明确的答复。

There's never been definitive proof that treatment with very bright lights makes a difference.

从来没有明确的证据表明，使用非常明亮的灯光进行治疗会有所不同。

This book is the definitive travel guide to Boston.

这本书是最好的波士顿旅游指南。

British definitives of low value merely have a portrait of the reigning monarch.

低价值的英国法定货币只印有在位君主的肖像。