worry 普通用词，着重使人焦虑、烦恼或深深不安。
brood 语气比worry强，多指沉思、沮丧或忧郁。
care 多指极强烈的关心和忧虑。常带纯客观的意味。
fret 通常指因悲哀、焦虑或忧愁等所困扰的心理状态。
参考例句
1. You are fretting yourself needlessly. 你在不必要地折磨自己。
2. We start to worry, fret, and be miserable much of the day. 我们开始担心、忧虑，大部分日子都过得很痛苦。
3. Worry and fret and irritation are emotions which serve no purpose. 担忧、烦恼和愤怒是不起任何作用的情感。
英英解释
n.
1. agitation resulting from active worry
2. a spot that has been worn away by abrasion or erosion
3. an ornamental pattern consisting of repeated vertical and horizontal lines (often in relief)
4. a small bar of metal across the fingerboard of a musical instrument; when the string is stopped by a v.
1. worry unnecessarily or excessively
2. be agitated or irritated
3. provide (a musical instrument) with frets
4. become or make sore by or as if by rubbing
5. cause annoyance in
6. gnaw into; make resentful or angry
7. carve a pattern into
8. decorate with an interlaced design
9. be too tight; rub or press
10. cause friction
11. remove soil or rock
12. wear away or erode
