agent

1) Any person appointed by another (the principal) to act on his or her behalf. See agency relationship

2) In contract law, a person appointed by a principal to negotiate a contract between the principal and a third party. If an agent discloses the principal's name (or at least the existence of a principal) to the third party in the transaction, the agent is not normally liable on the contract. An undisclosed principal, whose existence is not revealed by the agent to a third party, may still be liable on the contract, but in such cases the agent is also liable. However, an undisclosed principal may not be entitled to the benefit of a contract if the agency is inconsistent with the terms of the contract or if the third party has expressed a wish to contract with the agent personally. In law, agents are either general agents or special agents. A general agent is one who has authority to act for the principal in all business of a particular kind, or who acts for the principal in the course of the agent's usual business or profession. A special agent is authorized to act only for a special purpose that is not in the ordinary course of the agent's business or profession. The principal of a general agent is bound by acts of the agent that are incidental to the ordinary conduct of the agent's business or the effective performance of the agent's duties, even if the principal has imposed limitations on the agent's authority. But in the case of a special agent, the principal is not bound by acts that are not within the authority conferred. In either case, the principal may ratify an unauthorized contract. A commercial (or mercantile) agent selling goods on behalf of the principal sometimes agrees to protect the principal against the risk of the buyer's insolvency. Such an agent is called a del credere agent

3) A software program that can assist computer users to perform such tasks as finding particular types of information, for example, the best price for a product.