In American contract law, a person who does not reply to an offer has, in most cases, not accepted it. New Mexico’s standard jury instruction states the rule plainly: “Silence is acceptance only under [one or more of] the following condition[s].”
The conditions are narrow. In the first, the person took the benefits of the offer and knew that payment was expected. In the second, the offer gave the person reason to understand that silence could count, and the person meant to accept. In the third, past dealings between the two sides made silence a reasonable way to accept.