guarantee

ot noun

1. Anything that assures a certain outcome. Can you give me a guarantee that he will be fit for the match?
2. More specifically, a written declaration that a certain product will be fit for a purpose and work correctly; a warranty The cooker comes with a five-year guarantee.
3. A legal assurance of something, e.g. a security for the fulfillment of an obligation.
4. The person to whom a guarantee is made.

fe’l verb

1. To make something certain. The long sunny days guarantee a good crop.
2. To give an assurance that something will be done right.
3. To assume or take responsibility for a debt or other obligation.