Abbreviation for
absolute 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(32 + 42) = sqrt(25) = 5
abs((5,8,2,1)) = sqrt(52 + 82 + 22 + 12) = sqrt(94) = 9.695359...