1.NounA homogeneous polynomial of degree 2 in a given number of variables.
2.NounA scalar quantity of the form
ε
T
Λ
ε
{\displaystyle \varepsilon ^{T}\Lambda \varepsilon }
, where
ε
{\displaystyle \varepsilon }
is a vector of n random variables, and
Λ
{\displaystyle \Lambda }
is an n-dimensional symmetric matrix.