Fetching details from the dictionary...

to forget; to leave carelessly; to be forgetful of; to forget about; to forget (an article)
傘を忘れてしまった。
I forgot my umbrella.
約束の時間を忘れないでね。
Don't forget the appointment time.
あの日のことは一生忘れられないと思う。
I think I'll never forget that day.