worth, worthy, worthwhile都是形容词，意为"值得"。
1. worth： be worth + n. 当名词为金钱时，表示"…… 值得……"
常见的有It ’s worth while to do./ It ’s worth（someone’s）while doing
be worth doing sth. "……某事值得被做"
The question is not worth discussing again and again. 这问题不值得反复讨论。
2. worthy：be worthy of +n. 当名词为抽象名词时表示"……值得……"
be worthy to be done "某事值得被做"
The question is not worthy to be discussed again and again.
3. worthwhile： be worthwhile to do sth "值得做某事"
It is worthwhile to ask him to join the club.值得邀请他加入俱乐部。
典型例题
It is not ____ to discuss the question again and again.
A. worth B. worthy C. worthwhile D. worth while
答案C. 由worth的用法可知，此句只适合词组be worthwhile to do sth.。选C。