Linked from
The 15 pages that link to Discriminant (polynomial), each with the reason it gives.
Multiplicity of a rootRelated: It detects multiplicity without explicitly finding the roots.
Cubic equationRelated: The cubic discriminant reveals whether roots repeat and how many are real.
Branch pointRelated: For algebraic functions, its zeros commonly mark values where branches collide.
Algebraic functionRelated: Its zeros locate inputs where distinct algebraic branches can merge.
Sign (mathematics)Related: Its sign distinguishes the real-root cases of a quadratic equation.