👉 An extremal is a term used in mathematics to describe a quantity that is "most" or "least" (or both) when considered relative to some other quantity. In other words, it's something that is greater than its minimum value and less than its maximum value. For example, consider the function f(x) = x^2 - 4x + 3. This function has a maximum value of 3 at x=1, but it also has a minimum value of -