For an algebraic number field K, a quantity of this name determines which primes ramify K and equals the determinant (10[1])of a trace pairing matrix. For a polynomial, this noun denotes the product of all squared differences between pairs of roots. This noun appears in the name of a supervised learning method that finds weighted sums of features that maximize the ratio of between and within-class variances; that linear method was developed by Fisher. A complicated quantity of this name that includes the term “27 a-squared d-squared” appears in the innermost square root (10[1])in Cardano’s (10[1])formula. (10[1])The sign of a quantity of this name determines the number of roots of a quadratic polynomial. For 10 points, what noun denotes the quantity “b-squared minus (10[1])4 a c” (10[1])in the quadratic formula? ■END■