Aphe'lion. n.s. aphelia, plur. [from ἀπο, and ἥλιος, the sun.] That part of the orbit of a planet, in which it is at the point remotest from the sun.
The reason why the comets move not in the zodiack, is, that, in their aphelia, they may be at the greatest distances from one another; and consequently disturb one another's motions the least that may be. Cheyne's Philosoph. Principles.