Linear algebra

Vector norm

A norm assigns a nonnegative size to a vector and satisfies definiteness, homogeneity, and the triangle inequality.

Ask the Linear algebra assistant 1 min read · Updated September 9, 2026

Definition

A norm assigns a nonnegative size to a vector and satisfies definiteness, homogeneity, and the triangle inequality.

Intuition

The choice of norm determines what counts as a large vector or error.

Worked example

For (3, 4), the L2 norm is 5 and the L1 norm is 7.

The math

∥x∥2=∑ixi2\|x\|_2=\sqrt{\sum_i x_i^2} and ∥x∥1=∑i∣xi∣\|x\|_1=\sum_i|x_i|.

In machine learning

Norms measure residual error, regularize model weights, and normalize embeddings.

Go deeper

Sources

More in Linear algebra

Assembled from the ReLU.chat curated knowledge base. These explanations are concise on purpose; check the sources for anything important.