absolute value

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The numerical value of a real number without regard to its sign. For example, the absolute value of -4 (written }-4}) is 4. Also called numerical value.
2. n. The modulus of a complex number, equal to the square root of the sum of the squares of the real and imaginary parts of the number.

Wiktionary

1. n. mathematics For a real number, its numerical value without regard to its sign; formally, -1 times the number if the number is negative, and the number unmodified if it is zero or positive; the distance of a quantity from zero on a number line.
2. n. mathematics For a complex number, the square root of the sum of the squares of its real and imaginary parts.

WordNet 3.0

1. n. a real number regardless of its sign