In mathematics, what is the term for a number's distance from zero on a number line, expressed as a non-negative value?

Absolute value

Absolute value focuses purely on the magnitude of a number, ignoring its direction or sign. It is visually represented by two vertical bars, such as |-5| = 5. A helpful way to remember this is to think of distance; just as you cannot travel a negative distance to a destination, an absolute value can never be negative.