(n.) A quantity to be applied in computing the mean place or other element of a celestial body; that is, any one of the several quantities to be added to, or taken from, its position as calculated on the hypothesis of a mean uniform motion, in order to find its true position as resulting from its actual and unequal motion.
EQUATION
Meaning of EQUATION in English
Webster's English dictionary. Английский словарь Webster. 2012