any definite expression of acceptance, incuding conduct, shows intention to K is sufficient. Between merchants, additional terms become part of K unless materially alter K, offer limits acceptance of its terms, or objects in reasonable time. Even if some terms left open, K for sale of goods wont fail. K will not be enforced for more than the quantity specified. Essential term. When parties communication don't reflect K, K may be formed by conduct by delivery and acceptance of goods or by payment and acceptance.