前者担心
后者惧怕
1. 害怕的,怕的[(+of)][+to-v][+(that)]
She was afraid that she might lose her job.
她担心会丢掉工作。
It seems that she is afraid to tell them about it.
似乎她怕将此事告诉他们。
Don't be afraid of snakes.
别怕蛇。
2. (用于提出异议,告诉不好的消息等场合,使语气婉转)恐怕,遗憾[+(that)]
I'm afraid your wife had an accident.
很遗憾,你妻子出事了。
I'm afraid I can't help you.
对不起,我不能帮你。
后者
frightened
KK: []
DJ: []
a.
1. 受惊的
2. 【口】害怕的
He is frightened
参考资料：百度词典