Offer, defined in Section 2(a), is a proposal by one party (offeror) to another (offeree) expressing willingness to enter into contract on specified terms. Offers must communicate intent to be legally bound; mere invitation to treat or advertising is not an offer. Key elements: (1) Expression of willingness, (2) Definite terms, (3) Made with intention to be legally bound, (4) Communicated to another. Types: Express offer (clearly stated) and Implied offer (inferred from conduct). Offers differ from Invitations to treat (inviting offers, like store displays). Case law: Carlill v. Carbolic establishes that specific unilateral offers are valid. Termination: Offers lapse on specified date, rejection by offeree, counter-offer, death/insanity of offeror, or passage of reasonable time. An offer becomes a contract only upon acceptance. For accountants, service offers to clients must contain clear terms regarding scope, fees, and deliverables. Exam tip: Distinguish offers from invitations to treat; identify offer termination circumstances before concluding acceptance cannot form contract.