Final answer:
A special agent is a type of agent that represents one client, often in business or legal contexts, with authority limited to specific transactions, unlike a general agent with broader responsibilities.
Step-by-step explanation:
A single agent that represents one client is commonly known as a special agent in business and legal contexts. In the entertainment industry, for example, a special agent may represent an actor and is responsible for pitching that actor to a casting director for specific roles or projects. The term 'special' signifies that the agent's authority is limited to a particular transaction or set of transactions. Unlike a general agent, who has a broader, ongoing authority to conduct a range of transactions on behalf of a client, a special agent's role is more targeted and limited in scope.