①正当防卫，其英文表达为“justifiable defense”或“legitimate defence”指对正在进行不法侵害行为的人，而采取的制止不法侵害的行为，对不法侵害人造成损害的，属于正当防卫，不负刑事责任。

《中华人民共和国刑法》第二十条：

An act that a person commits to stop an unlawful infringement in order to prevent the interests of the State and the public, or his own or other person's rights of the person, property or other rights from being infringed upon by the on-going infringement, thus harming the perpetrator, is justifiable defence, and he shall not bear criminal responsibility.

为了使国家、公共利益、本人或者他人的人身、财产和其他权利免受正在进行的不法侵害，而采取的制止不法侵害的行为，对不法侵害人造成损害的，属于正当防卫，不负刑事责任。

②防卫过当，其英文表达为“excessive defence”或“unjustifiable self-defense”，是指防卫行为明显超过必要限度造成重大损害的应当负刑事责任的情形。所谓防卫过当是指正当防卫行为超越了法律规定的防卫尺度，因而应当负刑事责任的情况。在鼓励公民更好地利用防卫权，保护合法权益，维护社会秩序方面，有其积极的意义。

《中华人民共和国刑法》第二十条：

If a person's act of justifiable defence obviously exceeds the limits of necessity and causes serious damage, he shall bear criminal responsibility; however, he shall be given a mitigated punishment or be exempted from punishment.

正当防卫明显超过必要限度造成重大损害的，应当负刑事责任，但是应当减轻或者免除处罚。

If a person acts in defence against an on-going assault, murder, robbery, rape, kidnap or any other crime of violence that seriously endangers his personal safety, thus causing injury or death to the perpetrator of the unlawful act, it is not undue defence, and he shall not bear criminal responsibility.

对正在进行行凶、杀人、抢劫、强奸、绑架以及其他严重危及人身安全的暴力犯罪，采取防卫行为，造成不法侵害人伤亡的，不属于防卫过当，不负刑事责任。

【总结正当防卫和防卫过当的区别】：

1、正当防卫必须是没有明显超过必要限度，防卫行为必须在必要合理的限度内进行，否则就构成防卫过当。

2、正当防卫不负刑事责任，也就是不构成犯罪，而防卫过当需要负刑事责任。

参考双语例句：

While the ashes were still smouldering and the rubble of the Twin Towers still lay where it fell, the war in Afghanistan was launched, which, although perhaps justified as a case of legitimate defence, has nevertheless produced more victims than the terrorist attacks themselves.

在烟雾仍未散尽、双子塔仍是一片废墟的时候，阿富汗战争爆发了，虽然可能有理由说这是正当防卫，但是它所产生的受害者却比恐怖主义袭击本身还多。

Signatory Companies will require that their Personnel not use firearms against persons except in self-defence or defence of others against the imminent threat of death or serious injury, or to prevent the perpetration of a particularly serious crime involving grave threat to life.

各签字公司将要求其员工不对他人使用火器，但正当防卫、保护他人免受迫近的死亡或严重伤害威胁、以及防止实施确会带来死亡危险的特别严重罪行的情况除外。

The core objective of the establishment of the United Nations at the end of the Second World War was to maintain international peace and security, as stated in Article 1 of the Charter, and to deter and punish any State that chooses the military option except in cases involving collective security and legitimate defence

在第二次世界大战结束时建立联合国的核心目标是如《宪章》第一条中指出的那样维护国际和平与安全，以及威慑和惩罚任何在涉及集体安全和正当防卫的情况外选择军事办法的国家。