protect、defend、guard和safeguard这四个动词的意思都是“保护起来免受损害、伤害或袭击”的意思，但用法有些不同。

1.protect是最一般的常用词，它指提供保护免受伤害或毁坏。比如：Zinc is used to protect other metals from corrosion.锌被用来保护其他金属免受腐蚀。It's important to protect my fair skin from the sun.保护我白皙的皮肤不受日晒是很重要的。Players must wear padding to protect them from injury.运动员们必须戴上护垫以保护自己不受伤害。

2.guard 指“保护；守卫；护卫”，多指用极度的小心和戒备来防备危险或者潜在的危险。比如：

The dog was guarding its owner's luggage.狗守护着主人的行李。The political leaders were guarded by the police.政界领袖们由警方保卫。

3.safeguard 指“保护；保卫；保障；捍卫”，它多指保护某物或某人，保护他们不受伤害、丢失或虐待。多指遥远的将来的危险。这种保护或者防备是深谋远虑的。比如：

The leaflet explains how to safeguard against dangers in the home.小册子告诉人们在家里如何防备各种危险。We must safeguard our motherland.我们必须保卫我们的祖国。You can safeguard the information.你可以对信息进行安全地保护。

4.defend指“防御；保护；保卫”，多强调目前面临的危险，去用武力或其它对策进行保护。另外，defend也指坚持或维护行动、意见、决定等来防御责难、惩罚或不友好的评论比如：

All our policemen are trained to defend themselves against knife attacks.我们所有的警察都接受过自卫训练，能够对付持刀袭击。It is impossible to defend against an all-out attack. 防御全面进攻是不可能的。

Now that you are able to take up arms and defend your motherland, we are all proud of you.你现在能拿起武器，保卫祖国，我们都为你感到自豪。Troops have been sent to defend the borders.已派出部队去守卫边疆。

He defended his right to hold his political views.他坚持其政治观点保护其权利。A lawyer defending his client in court.律师在法庭上为其当事人辩护。

比较起来，defend和guard所指的避开危害的成功率没有protect那么高。一个人可能徒劳地guard或者defend一个人或一件事，但如果一个人protect一个人或一件事，那么可能会很安全的。