**abs**olute value, usually meaning the length of a vector, be it a one-dimentional number, a two-dimentional complex number, or any n-dimentional vector. The absolute value of the vector v is written abs(v) or |v|. Some examples:

abs(-42) = 42

abs(3.14) = 3.14

|(3,4i)| = sqrt(3^{2} + 4^{2}) = sqrt(25) = 5

abs((5,8,2,1)) = sqrt(5^{2} + 8^{2} + 2^{2} + 1^{2}) = sqrt(94) = 9.695359...