To inform or notify someone of something; to convey information, decisions, or news so that someone becomes aware.
結果が出たらすぐに知らせてください。
Please let me know as soon as the results are out.
会議の時間が変わったら、全員に知らせる必要がある。
If the meeting time changes, it's necessary to inform everyone.
彼は病気で来られないと電話で知らせてきた。
He called to inform me that he couldn't come because he was sick.