invariantfunction
nounUK /ɪnˈveəriənt ˈfʌŋkʃən/
US /ɪnˈveriənt ˈfʌŋkʃən/
A function is invariant when it gives the same answer even after you change something else.
The area of a shape is an invariant function under rotation, because spinning the shape does not change its area.
OTHER MEANINGS
2. In mathematics, a function whose value stays the same under a particular group of transformations.
The distance from the center is an invariant function under rotations of the circle.
3. In physics, a quantity computed by a function that does not change when the reference frame changes.
Rest mass is an invariant function of a particle's four-momentum.
4. In computer science, a function whose output depends only on its inputs and not on hidden state.
A pure function is invariant with respect to the order in which it is called.