Lines or planes that are equidistant from each other and do not intersect: Any perpendicular distance between parallel lines or planes is the same at any location.

Sally's mother bought her an exercise book with parallel line for her German class.

The rails of a train track are always parallel to each other!

A way of joining solar cells or photovoltaic modules by connecting positive leads together and negative leads together; such a configuration increases the current, but not the voltage.