An Etymological Dictionary of Astronomy and Astrophysics

1. Said of two or more things, such as lines or planes, that are equally distant from one another at all points.
   
2. Electricity: An arrangement of the components in an electric circuit so that the same voltage is applied to each component. Compare → series.
   

Etymology (EN): From M.Fr. parallèle, from L. parallelus, from Gk. parallelos “parallel,” from para allelois “beside one another,” from → para- “beside” + allelois “each other,” from allos “other,” → alias.

Etymology (PE): Parâsu, from parâ-, → para-, + su “direction, side,” from Mid.Pers. sôk “direction, side.”