A quick reference describing the difference between technical, functional and system specifications. This helps when defining responsibility and accountability amongst teams working on projects or operations.
Technical specifications is a broad term. It describes any characteristic of an engineered system that must conform to a specific metric, within some degree of error.
Functional specifications describe the expected behavior of a system.
System specifications describe what the system is supposed to achieve. This differs from a functional specification in that, while a system specification describes what the system does, the functional specification will describe the manner in which it does it.