The ratio of system variation to input effort.
Configurability is that quality allowing system behavior to be varied by a small amount of user input. The more configurable a system is:
1. The easier it is to build and modify.
2. The more of this the user can do.
3. The higher reuse is.
4. The cheaper the system is.
5. The faster it can be built.
6. The more defect free it tends to be.