R2d § 3
Agreement Defined; Bargain Defined
An agreement is a manifestation of mutual assent on the part of two or more persons. A bargain is an agreement to exchange promises or to exchange a promise for a performance or to exchange performances.
Professor's notes
Two definitions in one section. (1) An agreement is mutual assent by two or more persons. (2) A bargain is the narrower category: an agreement to exchange: promise for promise, promise for performance, or performance for performance. Every bargain is an agreement; not every agreement is a bargain.
Hamer v. Sidway operationalizes the bargain category: uncle's promise was made in exchange for the nephew's forbearance from drinking and smoking. Exchange, not affection, is what makes the promise enforceable.
Common misunderstanding: students treat "agreement" and "bargain" as synonyms. They are not. A gift promise is an agreement (both parties assent) but not a bargain (no exchange sought). Section 71's consideration requirement attaches to bargains. The agreement-bargain distinction is the entry point to the whole consideration doctrine.
Cases that operationalize this rule
Section 3 distinguishes the broader idea of agreement from the narrower category of bargain. That distinction matters because many doctrines, especially consideration, depend on whether the parties exchanged commitments or performances. The provision thus links assent analysis to the architecture of enforceability.