True contractors have a specific blood type. It is a different blood type from that of a consultant, but a blood type none the less. True contractors also are distinguished from people who work on a contract while between full-time employees (contractor by convenience). I differentiate contractors from consultants by a simple rule of thumb. An organization will hire a consultant to advise them on a course of action. An organization will hire a contractor (or many) as a source of external labor to execute against a pre-defined plan. In the IT arena roles of project manager and programmer are frequently filled by contractors.