doubt

I have some doubt about whether his story is really true.

彼の話が本当に真実なのか、私には少し疑念があります。

There is no doubt that she worked harder than anyone else on the project.

彼女がそのプロジェクトで誰よりも一生懸命働いたことは疑いの余地がない。

He began to doubt his decision after hearing the bad news.

悪い知らせを聞いて、彼は自分の決断を疑い始めた。