compel, constrain, force, oblige这一组动词都有“强迫”的意思。
oblige v. (因法律、习俗等)强迫，迫使，常常用于被动。
We are obliged to stop the car at a red light.
我们遇到红灯时必须停车。
compel v.强迫，迫使，常表示运用权利、力量迫使对方做某事;
有时也表示"别无办法，不得不做"。
His illness compelled him to stay in bed. 他的病迫使他卧床休息。
constrain v.力劝，强迫，与compel意思相近，但更多强调内心情感(如道德、怜悯等)的强迫和限制作用，一般用于正式的场合。
As an artist he didn't consider himself constrained by the same rules of social conduct as other people.
他认为自己是艺术家，不必象一般人那样要受到社会行为准则的约束。
force v.强迫，迫使，暴力威胁的意味较浓，常用于被动语态。
The thief forced her to hand over the money.
强盗逼迫她把钱交出来。