二者作“害怕”之义时,可互换,如：
I'm afraid/ (scared) of dogs.我害怕狗.
但scare多用“恐吓”“惊吓”“惊恐”解.
如：The dog scared the thief away.那狗把贼吓得要死.
be scared to death 吓得要死
The house scares easily.马易受惊.
而afraid是形容词,常作表语,“担心的”“害怕的”“恐怕”.
I'm afraid I'm late.恐怕我晚了吧.
He was afraid that he would fail.他担心他会失败.