@minogully@mstdn.ca They might have some specific definition of "constant" in mind, or some specific situation or usage.

Just for example, in a polynomial expression we often write it with constants denoted like a, b, c and the variable is x. So ax^2 + bx + c.

That type of constant is a different thing than pi, even though we typically use the same word to describe them. Like if you wrote ax^2 + bx + pi, that mean something different than ax^2 + bx + c.

But still, that is sort of a strange thing to just blurt out randomly without taking the time to give a full explanation. Just for example, pi is one of the first specific examples given in the Wikipedia article on mathematical constants: https://en.m.wikipedia.org/wiki/Constant_(mathematics)