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. I found her in her house,brooding on(或over) her failure to get a job after a year of trying. 我发现她呆在房子里，郁闷地沉思她经一年努力后仍找不到工作之事。
2. A hen and her brood (of chicks) . 母鸡和它的一窝小鸡。
3. There are twelve chickens in this brood. 这一窝共孵出了十二只小鸡。
英英解释
n.
1. the young of an animal cared for at one time
2. think moodily or anxiously about something
3. hang over, as of something threatening, dark, or menacing
4. be in a huff and display one's displeasure
5. be in a huff; be silent or sullen
6. sit on (eggs)
