If someone behaves strangely, they do something unusual or unexpected and make you feel slightly nervous or afraid.
She noticed he was acting strangely.
她注意到他行为怪异。
You use strangely to emphasize that what you are saying is surprising.
Strangely, they hadn't invited her to join them.
令人奇怪的是,他们竟没邀请她参加。