Noun:

1. the act of defending yourself

self-protectionn.自卫；自我保护

self-preservationn.自卫本能

defencen.防御；答辩；防务

resistancen.抵抗；抵触；反对；阻力n.[电]阻抗

self-defensen.自卫；[法]正当防卫

1. He said that he killed the man in self defence.
   他说是因自卫而杀死那个人的。
2. A weapon carried for self defence is quite different.
   以自卫为目的携带的武器有很大区别。