semi-norm

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• noun 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.