He is afraid to go out / of going out alone at night.
3) 担心会发生某事, 如: be afraid of doing sth或be afraid + that clause
He seldom stands on the river bank because he is afraid of falling into the river.
He seldom stands on the river bank because he is afraid that he might fall into the river.
4) 给人不愉快的信息或不赞同某人意见时, 用I’m afraid …, 如: I’m afraid I’ve got bad news for you.
I’m afraid I can’t agree with you.