Witt's theorem

Witt's theorem is an important result in the theory of quadratic forms in mathematics, specifically in the context of algebraic groups and linear algebra over fields. It provides a characterization of the equivalence of quadratic forms over fields. In simpler terms, Witt's theorem states that any two non-degenerate quadratic forms over a field can be transformed into each other by means of an appropriate change of variables, if and only if they have the same "Witt index" and the same "discriminant".