Also known as hypothecation. The transferring of property (but not title to the property) by an entity to a lender or creditor as collateral to secure payment or performance of an obligation.

A pledge agreement is just another name for a security agreement which creates a security interest in equity and promissory notes. The term "pledge" predates the UCC, when a pledge involved the creation of a security interest by physical possession of the property. Under the UCC, a pledge agreement is a security agreement.