doubt多数情况作不可数名词，意思为：怀疑。eg.There is no room for doubt.有时也作可数名词，意思为：怀疑的念头、疑虑等。eg.A sudden doubt came to his mind.

双语例句

I doubt he ever voted for me.

我怀疑他可能从未投过我的票。

Why do you doubt me?

为什么你怀疑我？

But I doubt it.

但是我怀疑它。