1. Law: (1) A party who designates another (the agent) to act on his or her behalf. (2) A party that has the primary responsibility in a liability or obligation, as opposed to an endorser, guarantor, or surety. (3) A person who commits a crime, takes an active part in its commission, or directly or indirectly counsels or procures another person to commit it. 2. Commerce: A major party in a business transaction. 3. Contracts: A client who awards a contract to a contractor for completion of a job or project in accordance with terms of the contract. Also called owner. 4. Finance: Capital as distinct from the income (interest) derived from it. 5. Securities: The par value of a security.