close beside, or corresponding to: one thing set directly parallel to another, in space or in kind
This word draws a picture of two things lined up next to each other. It almost always appears with a small attached word (forming le-ummat), and it answers the question next to what, or matching what. Its whole meaning grows out of that single image of things running parallel.
In its plainest use the parallel is physical. One object sits alongside or straight across from another: the gold rings set opposite the frame of the tabernacle, the wheels in Ezekiel's vision moving in step beside the living creatures, or Shimei walking along the ridge across the valley from David while he curses him.
From that picture of things side by side comes the second use, where the parallel is not in space but in kind. One thing corresponds to, matches, or answers to another. Ecclesiastes says that exactly as a person came into the world, so he leaves it, and that God has set good days and hard days to answer one another. The two uses are really one idea, parallelism, seen once with the eye and once with the mind.