whom可以引导名词性从句(主语从句、宾语从句、表语从句、同位语从句)和定语从句，在这些从句里都是作宾语成分。例句如下:

Whom she saw didn't matter.她看见了谁不重要。(主语从句)

I know whom he loves.我知道他爱谁。(宾语从句)

What I care most is whom he loves best.我最关心的是他最爱谁。(表语从句)

He didn't answer the question whom he got help from.他没有回答他得到谁的帮助的问题。(同位语从句)

Mother is the person he misses most.妈妈是他最想念的人。(定语从句)