What are the similarities and differences? I already know about (and therefore am not asking about) a reserved number of definitions unique to each noun, but what about the following definitions that look alike?
agency = 1. [often with adjective or noun modifier] A business or organization providing a particular service on behalf of another business, person, or group
= 2. [mass noun] Action or intervention producing a particular effect
agent = 1.2. A person or company that provides a particular service
2. A person or thing that takes an active role or produces a specified effect: