APHELION, in astronomy, that point of the orbit of a planet at which it is most distant from the sun. Apogee, apo centre, aposaturnium, etc. are terms applied to those points of the orbit of a body moving around a centre of force—as the earth or Saturn—at which it is farthest from the central body. APHEMIA, in pathology, the loss of the power of speech (see APHASIA).