A demonstration of the willingness of a party to enter into a bargain, made in such a way that another individual is justified in understanding that his or her assent to the bargain is invited and that such assent will conclude the bargain. The general rule is that it must be reasonable in the circumstances for the recipient to believe that the communication is an offer. The more definite the communication, the more likely it will constitute an offer.

A formal promise by one party (the guarantor or surety) to another party (the creditor) to accept responsibility of a third party’s (the principal debtor) debt, if that third party cannot or refuses to pay it.