"Vertical" means that something is in an up and down position, or standing upright. In math terms, it is defined as something in a position that is perpendicular to the plane or horizon. In botany, a vertical leaf sits on a perpendicular plane with no upper or lower surface.
The perpendicular or horizontal plane on which a vertical object sits is known as the horizon. On a graph, the horizon normally is the X-axis, and the vertical axis is the Y-axis.
The term "vertical" also relates to a the process of executing or delivering a product or service from the initial planning stage to sale. It also describes up or down movement within a stratified society or nation.