quadratic form

noun2

1. •
   A homogeneous polynomial of degree 2 in a given number of variables.

   • Historically, quadratic form theory has been treated as a rich but misunderstood uncle. — 1980
2. •
   A scalar quantity of the form εᵀΛε, where ε is a vector of n random variables, and Λ is an n-dimensional symmetric matrix.

   • Quadratic forms of normal random vectors are of great importance in many branches of statistics, such as least-squares methods, the analysis of variance, regression analysis, and experimental design. — 2009