The ability to do a task, performance, or execution; a set of functions that something is able or equipped to perform.
The presence of a functional group.
In United States trademark law, the tendency of a product design to serve a function other than identification of the product, preventing that design from being protected as a trademark.
The state or condition of being usable.
The degree to which an object, device, software application, etc. is easy to use with no specific training.