Agent vs. Reagent

One that acts or has the power or authority to act.

A substance used in a chemical reaction to detect, measure, examine, or produce other substances.

One empowered to act for or represent another

(chemistry) A compound or mixture of compounds used to treat or test materials, samples, other compounds or reactants in a laboratory or sometimes an industrial setting.

A means by which something is done or caused; an instrument.

A substance capable of producing with another a reaction, especially when employed to detect the presence of other bodies; a test.

A force or substance that causes a change

A chemical agent for use in chemical reactions

A representative or official of a government or administrative department of a government

A spy.

(Linguistics) The argument that expresses the means or cause of an action or event described by a phrase or clause. The noun John is the agent in the clause John threw the ball.

To act as an agent or representative for

To act as an agent or representative.

One who exerts power, or has the power to act

One who acts for, or in the place of, another (the principal), by that person's authority; someone entrusted to do the business of another

A person who looks for work for another person

Someone who works for an intelligence agency

An active power or cause or substance; something (e.g. biological, chemical, thermal, etc.) that has the power to produce an effect

(computing) In the client-server model, the part of the system that performs information preparation and exchange on behalf of a client or server. Especially in the phrase “intelligent agent” it implies some kind of autonomous process which can communicate with other agents to perform some collective task on behalf of one or more humans.

(grammar) The participant of a situation that carries out the action in this situation, e.g. "the boy" in the sentences "The boy kicked the ball" and "The ball was kicked by the boy".

(gambling) A cheat who is assisted by dishonest casino staff.

Acting; - opposed to patient, or sustaining, action.

One who exerts power, or has the power to act; an actor.

One who acts for, or in the place of, another, by authority from him; one intrusted with the business of another; a substitute; a deputy; a factor.

An active power or cause; that which has the power to produce an effect, such as a physical, chemical, or medicinal agent; as, heat is a powerful agent.

A chemical substance having biological effects; a drug.

An active and efficient cause; capable of producing a certain effect;

A substance that exerts some force or effect

A representative who acts on behalf of other persons or organizations

A businessman who buys or sells for another in exchange for a commission

Any agent or representative of a federal agency or bureau

The semantic role of the animate entity that instigates or causes the hapening denoted by the verb in the clause