at risk 和in danger都是“有危险” 它们可以互换吗？是同义词还是近义词？

还是有区别的。

◆at risk（可能的危险）一意为threatened by uncertainties (such as failure, loss, etc)指可能遭到失败，损失等意。比如：

1、Is the government’s income tax policy seriously at risk? （政府的税收政策有可能招来大损失？）

2、The disease is spreading, and all children under 5 are at risk. （疾病正在蔓延,所有五岁以下的小孩都有被传染的危险。）

3、These measures will put many small businesses at risk.（这项政策将威胁到很多小企业的生存）

◆in danger（现实的危险）意为“处境危险”，“遇险”，例如：

1、He was in danger of losing his life. （他那时生命危在旦夕）：

2、The girl's life was obviously in immediate danger. （很明显,这女孩的生命危在旦夕。）

3、We were in danger of being hit by a stone.（我们有随时被石头砸伤的危险。）

4、承运人在运输过程中，应当尽力援助患有急病、分娩、遇险的旅客。（中华人民***和国合同法301条）

A carrier shall, during the period of carriage, render whatever help and assistance as it can to passenger who is seriously ill, or who is giving birth or whose life is in danger.（The People's Republic of China Contract Law article301）

一般来说，正当防卫的前提是存在现实危险；但当代有人把防卫对象提前到“潜在的危险”，这就是英美国家的“先发制人”理论。

In general, the premise of Self-defense is in danger situation; but the defense object has been forward to “at risk circumstance” at contemporary, this is the “preemptive” theory which Britain and U.S.A impose to other countries.