More generally: any equivalence relation defined on an algebraic structure which is preserved by operations defined by the structure.
The quality of agreeing or corresponding; being suitable and appropriate.
Matrix similarity by an orthogonal matrix.
A relation between two numbers indicating they give the same remainder when divided by some given number.
The quality of being isometric — roughly, the same measure and shape.
The set of values x for which a real-valued function f(x) is equal to a given constant.
An event consisting of level setting
A state of mutual understanding among parties
To establish a baseline of mutual understanding