Guarantee和warranty都是涉及产品或服务质量的常用词，两者异同如下：

1.Guarantee与warranty同源，都来自日耳曼语，后演变出不同拼法与含义。

2.Guarantee与warranty在不严格情况下是同义词。

3.Guarantee可以是口头或书面的，而warranty是书面的。

4.Guarantee与付费无关，而warranty与付款有关。

5.Guarantee和warranty可以同时存在。

6.Guarantee通常承诺退款，类似质保，而warranty通常只负责修理，类似保修。

7.Guarantee往往来自制造商，而warranty往往来自销售商。

8.Guarantee还有另一个写法为guaranty。历史上，前者为动词而后者为名词，但如今已差别不大，可作为同义词使用。如30-day money back guarantee 或30-day money back guaranty。

9.Guarantee通常没有时限，与质量有关，如lifetime guarantee，而warranty一般注明12个月或24个月等，并且可以延期。

A guarantee:
保证：

Is usually free通常是免费的
It's a promise to sort out any defects with a product or service within a fixed period of time
是项在固定期限内解决产品或服务的任何缺陷的承诺
It's a legally binding contract, even if you didn't pay for it
是项具有法律约束力的合同，即使你没有为此付出代价
It must explain how to go about making a claim in a way that is easy to understand
它必须以通俗易懂的方式解释如何进行索赔
It should add to, not take away from, your rights under consumer law
它应该增加，而不是剥夺，你在消费者保护法项下的权利
It works whether or not you have a warranty
不论您是否保修“保证”依然有效

A warranty:
保修：

A warranty is like an insurance policy for which you must pay a premium.
保修就像必须支付保费的保险政策。
Sometimes it's called an 'extended guarantee'.
有时它被称为“延期保证”
It might cover a longer period than a guarantee, and it might cover a wider range of problems.
它的期限可能比保证的期限要长，并可能包括更广泛的产品问题。
A warranty is a legal contract, so you can take the company to court if they don't honour it.
保修是个法律合同，这样如果公司不遵守你就可以向法院告他们。
The terms of the contract should be clear and fair.
合同的条款应当明确和公平的。
Having a warranty doesn't diminish your rights under consumer law.
保修并不削弱你在消费者保护法项下的权利
A warranty can run alongside a guarantee.
保修可以与保证同步进行