You can find them in English dictionaries
EnLearner
2011-09-04 07:58:50
( reads)
ob·sess 
/əbˈsɛs/ verb
/əbˈsɛs/ verb
ob·sess·es; ob·sessed; ob·sess·ing
1 [+ obj] : to be the only person or thing that someone thinks or talks about
▪ The war obsesses him—he talks about nothing else. — usually used as (be) obsessed ▪ He is obsessed by the war. ▪ She was obsessed with her weight. [=she thought about her weight all the time] ▪ She became more and more obsessed with the project.
▪ The war obsesses him—he talks about nothing else. — usually used as (be) obsessed ▪ He is obsessed by the war. ▪ She was obsessed with her weight. [=she thought about her weight all the time] ▪ She became more and more obsessed with the project.
2 [no obj] informal : to think and talk about someone or something too much
▪ You need to stop obsessing and just deal with the problem. — usually + about or over ▪ I'm trying to obsess less about my weight. ▪ He's always obsessing over money.
▪ You need to stop obsessing and just deal with the problem. — usually + about or over ▪ I'm trying to obsess less about my weight. ▪ He's always obsessing over money.
obsess [əbˈsɛs]
vb
1. (tr; when passive, foll by with or by) to preoccupy completely; haunt
2. (intr; usually foll by on or over) to worry neurotically; brood
[from Latin obsessus besieged, past participle of obsidēre, from ob- in front of + sedēre to sit]
Collins English Dictionary – Complete and Unabridged © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003
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2011-09-04 08:59:10谢谢愚公补充的重要信息。学到了更多表达法。