Definition of horizontal

The word "horizontal" has its roots in Latin and Old French. The Latin word "horizontalis" means "in a straight line, level" and is derived from the words "horum," meaning "line" or "border," and "tensor," meaning "stretch" or "extend." In the 15th century, the Latin term was borrowed into Middle French as "horizontal," with the same meaning. The term was first used in English in the 15th century to describe lines or surfaces that are parallel to the horizon, or the apparent line where the earth meets the sky. Over time, the term came to be used more broadly to describe any line or direction that is parallel to the horizon, whether it's a line on a graph, a direction of movement, or a vanishing point in perspective drawing. Today, "horizontal" is a common adjective used to describe many different concepts, from linguistics to architecture to physics.