The software comes with a 'money-back guarantee'. [=a promise that the money you spend on a product will be returned if the product is not good enough]
We used our house as a 'guarantee' for the loan. [=we said that the bank could take our house if we did not pay back the loan]
There is no 'guarantee' that they will approve the contract. [=there is no way to be sure that they will approve it]
(..) - I am afforded the right... to speak in my own defence, sir, by the Constitution of the United States. - This is the same document which guarantees my liberty. - Don't tell me about the Constitution of the United States. And liberty, in case you've forgotten, is a souI's right to breathe. (..)1997 Good Will Hunting