a. the characteristic polynomial of a given matrix, equated to zero.
b. Also called auxiliary equation. an equation with one variable and equated to zero, which is derived from a given linear differential equation and in which the coefficient and power of the variable in each term correspond to the coefficient and order of a derivative in the original equation.
2. Physics.See equation of state.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.