Noun
separable polynomial (plural separable polynomials)
(algebra, field theory) A polynomial over a given field that has distinct roots in the algebraic closure of said field (the number of roots being equal to the degree of the polynomial).
Over a perfect field, the separable polynomials are precisely the square-free polynomials.
The study of the automorphisms of splitting fields of separable polynomials over a field is referred to as Galois theory.