be afraid to do sth.意為膽怯某人（或某物），主語對做某事內心感到恐怖。be afraid of doing sth.意思是“膽怯做某事”，表示主語內心里不愿意做某事，也可以說是不希翼發(fā)生某事，但自己不一定能幸免它。

1. be afraid to do：這個詞組表達的是“膽怯做某事”，側重表示不敢的意思。

例句1：Tom is afraid to swim in the river.

湯姆不敢在河里游泳。

例句2：The boy was afraid to stay at home alone.

這個小男孩不敢獨自呆在家里。

例句3：Tom was afraid to answer questions at class.

湯姆不敢在課堂上回答問題。

2. be afraid of doing：這個詞組側重表達的是“擔心做某事的后果”。

例句1：People are afraid of getting left behind right now.

人們現(xiàn)在非常擔心被落下。

例句2：They may be afraid of losing you.

他們可能膽怯失去你。

例句3：Don't be afraid of making mistakes because everyone makes mistakes.

不要膽怯犯錯，因為每個人都會犯錯。

來源：高三網(wǎng)