The acceptance must be unequivocal and communicated to the offeror. Any material change in, or addition to, the terms of the original offer automatically terminates the offer and serves as a counteroffer. Sometimes, however, the offeree has a duty to speak in which case his silence or inaction will operate as an acceptance. For example, silence may be an acceptance when an offeree takes the benefit of offered services even though he had an opportunity to reject them and knew that they were offered with the expectation of compensation.
Silence can also operate as acceptance when the offeree has had prior dealings with the offeror.
Suppose, for example, a merchant routinely receives shipments from a supplier and always notifies the supplier when defective goods are rejected. His silence regarding a shipment will constitute acceptance. The offeree must communicate the acceptance to the offereor. However, the offer may dispense with the requirement of communication. If the offer is to enter into a unilateral contract, communication of acceptance is usually not necessary.