Customer

Defined: Anyone or anything that receives some {thing, service etc.} based on {a set of requirements, needs, desire etc.} from a unit that can deliver the {thing, service etc.} The term Customer mostly implicates at least one person or company that requires something, and at least one company that delivers something against payment. It can also be used internally ie. if the salesdivision in your company requires a change in an application from your software development division. In such cases the use of the 'Customer'-Contractor term often will improve the quality of the delivery because it's a clearly, concious statement saying that one internal division delivers a service to another, and that some degree of quality is required.