Emily Dickinson Lexicon

PAR'AL-LAX, n. [Gr. παραλλαξις, from παραλλασσω, to vary, to decline or wander, παρα, beyond, and αλλασσω, to change.]

In astronomy, the change of place in a heavenly body in consequence of being viewed from different points. Diurnal parallax, the difference between the place of a celestial body, as seen from the surface, and from the center of the earth, at the same instant. Annual parallax, the change of place in a heavenly body, in consequence of being viewed at opposite extremities of the earth's orbit.