Translation of "semi-norm" into Russian

(analysis) A function denoted || v || that maps a vector v to a non-negative value such that || cv || = | c |.|| v ||, where c is a scalar, and || v + w || ≤ || v || + || w || (the triangle inequality); the condition that || v || = 0 implies that v = 0 is not required, but when it holds, the semi-norm is a norm. [..]