What is the difference between equivalence and equ

Question

What is the difference between equivalence and equality in C++?

There is a very similar question here. However, this question is tagged with math, while I am interested in the meaning in C++ context.

To see the terms in context: Scott Meyers uses them in an example in this video.

Answer 1

On cppreference.com i found the following quote:

For the types that are both EqualityComparable and LessThanComparable, the C++ standard library makes a distinction between equality, which is the value of the expression a == b and equivalence, which is the value of the expression !(a < b) && !(b < a).