19 General utilities library [utilities]

19.14 Function objects [function.objects]

19.14.2 Definitions [func.def]

The following definitions apply to this Clause:
A call signature is the name of a return type followed by a parenthesized comma-separated list of zero or more argument types.
A callable type is a function object type or a pointer to member.
A callable object is an object of a callable type.
A call wrapper type is a type that holds a callable object and supports a call operation that forwards to that object.
A call wrapper is an object of a call wrapper type.
A target object is the callable object held by a call wrapper.
A call wrapper type may additionally hold a sequence of objects and references that may be passed as arguments to the target object.
These entities are collectively referred to as bound argument entities.
The target object and bound argument entities of the call wrapper are collectively referred to as state entities.