n. 1. a number,denoting whether a permutation differs from the natural order by an odd or even number of steps: ɛ = +1 if the permutation is even; ɛ = -1 if it is odd. See epsilon (sense 3). 2. (of an Hermitian matrix or quadratic form) the surplus of positive over negative coefficients in any real diagonal matrix or form similar to the given one; this equals the excess of positive over negative eigenvalues. See Sylvester's law of inertia.