worth，worthy，worth-while都為adj. 意為"值得"。
1. worth： be worth + n. 當(dāng)名詞為金錢時(shí)，表示"…… 值得……"
be worth doing sth. "……某事值得被做"
The question is not worth discussing again and again.
2. worthy：be worthy of +n. 當(dāng)名詞為抽象名詞時(shí)表示"……值得……"
be worthy to be done "某事值得被做"
The question is not worthy to be discussed againand again.
3. worth-while： be worth-while to do sth "值得做某事"
worth while： It is worth while doing sth
It is worth while sb to do sth.
典型例題
It is not ____ to discuss the question again and again.
A.worth B.worthy C.worth-while D.worth while
答案C. 由worth的用法可知，此句只適合詞組be worth-while to do sth.。因此選C。