suffocate: likely to imply the impossibility to breathe because of absence of oxygen, presence of noxious gases, or the interference with passage of air to and from the lungs: ~ under the sand which had fallen upon him.


asphyxiate: likely to refer to situations involving death through lack of oxygen or presence of toxic gas: several people were ~ by calorine escaping from the wrecked train.


stifle: is apppropriate for situations where breathing is difficult or impossible because of inadequate fresh air: the room's ~ atmosphere.


smother: usable in situations in which the supply of oxygen is inadequate for life, and often suggest a deandening pall of smoke, dust or impurities in the air: ~ by a blanket of volcano ash.


choke: suggests positive interference with breathing, for example by compression, obstruction, or severe inflammation of throat: ~ on a bit of apple.


strangle: similar to choke, more consistently imply a serious or fatal interference: ~ to death by the assailant.


suffocate: 无法呼吸<==缺氧毒气或气管堵塞, asphyxiate: 导致死亡的缺氧或毒气，stifle: 呼吸困难<==缺少新鲜空气, smother: 不足以维生<==空气充满烟尘等, choke: 专指阻碍呼吸(positive interference)，如挤压阻塞发炎等, strangle勒死: 更严重致命的阻碍呼吸。


记忆方法： 1) SAS SCS想成南非洲海South Africa Sea和南海South China Sea: 都是咽喉，阻塞会窒息。

           2) strangle最严重, suffocate,smother和asphyxiate也致命, choke和stifle较轻,表示阻碍呼吸和空气不新鲜。

           3）窒息的意思是阻断呼吸通道mean to interrupt the normal course of breathing.