agent

noun

• 1a person who acts on behalf of another, in particular.
• a person who manages business, financial, or contractual matters for an actor, performer, or writer.
• a person or company that provides a particular service, typically one that involves organizing transactions between two other parties:a travel agent shipping agents a real-estate agent
• a person who obtains information for a government or other official body, typically in secret:a trained intelligence agent KGB agents an FBI agent

• 2a person or thing that takes an active role or produces a specified effect:agents of change bleaching agents
• Grammar the doer of an action, typically expressed as the subject of an active verb or in a by phrase with a passive verb.