The absolute value of a number is its distance from 0 on the number line. Because distance is always at least 0, absolute value is always zero or positive — never negative.

For example, the absolute value of -4 is 4, because -4 is 4 units to the left of 0. The absolute value of 4 is also 4, because 4 is 4 units to the right of 0.

To write “the absolute value of a number”, we use two straight vertical bars around the number. So the absolute value of -5 is written $|\text-5|$, and we say $|\text-5| = 5$. Similarly, $|\text-12.9| = 12.9$ and $|\text-3.2| = 3.2$.

Opposites always have the same absolute value. The numbers -7 and 7 are opposites because they are both 7 units from 0, so $|\text-7| = |7| = 7$. The distance from 0 is the same no matter which side of 0 the number is on.

The only number whose distance from 0 is 0 is 0 itself, so $|0| = 0$.