DEFERENT

(Lat. defero, / carry away.) In the Ptolemaic system of the universe the planets move in circular orbits, the centres of which are carried round in the circumferences of other circles. These secondary circles are called the deferents, as carrying the orbits: those in which the planets move being the epicycles. The system of epicycles and deferents was invented by Hipparch us for the purpose of explaining the eccentricities, perigees, and apogees of the planets. See Epicycle. DEFICIENT NUMBERS, in Arithmetic, are numbers such that the sum of their aliquot parts is le than the numbers themselves. Thus, 8 is a deficient number; because its aliquot parts, 1, 2, 4, when added together, make only 7. In like manner the number 16 is deficient, its narU being 1, 2, 4, 8, the sum of which is 15. [s. 336]