Acceptance, defined in Section 2(b), is the offeree's unconditional agreement to all terms of an offer. Key principles: (1) Acceptance must be unconditional—conditional acceptance is a counter-offer; (2) Acceptance must be communicated to offeror; (3) Acceptance must be given before offer terminates; (4) Acceptance can be express (stated) or implied (inferred from conduct). Communication of acceptance varies by offer—if offer specifies acceptance method, that method must be used. Acceptance by post is complete when letter is posted, not when received (Adams v. Lindsell principle). Silence does not constitute acceptance unless parties' course of dealing suggests otherwise. Mental acceptance (mere intention) is insufficient—communication is required. Case law: Felthouse v. Bindley establishes silence without more does not create contract. Exceptions: Accepting benefits (receipt of goods) may imply acceptance. For accountants, client acceptance of engagement letters must be clearly communicated to avoid disputes. Exam tip: Check if acceptance was communicated before offer expired; distinguish acceptance from counter-offer.