by mistake (誤って): I took his umbrella by mistake. (彼の傘を誤って持ってきてしまいました。) - 試験に出る! 英単語検索辞書

by mistake (誤って): I took his umbrella by mistake. (彼の傘を誤って持ってきてしまいました。)

I took his umbrella by mistake.