Warranty

A warranty is used to guarantee the effectiveness of a product for a specified period of time. Consumers, of course, hope that the products they purchase actually serve their intended purpose; warranties ensure this.

Note the fine print though, as many warranties run only for a limited period of time. So if your $100 essential oil diffuser comes with a warranty, but you miss the fine print that states that your warranty only lasts 30 days, and a power surge breaks it two months later...you're S.O.L.