The terms zonal and meridional are used to describe directions on a globe. Zonal means "along a latitude circle" or "in the west–east direction"; while meridional means "along a meridian" or "in the north–south direction".
These terms are often used in the atmospheric and earth sciences to describe global phenomena, such as "meridional wind flow", or "zonal temperature". (Strictly speaking, zonal means more than simply a direction as it also implies a degree of localization in the meridional direction, so that the phenomenon in question is localized to a zone of the planet.)
"Meridional" is also used to describe the axis close to the chain orientation in a polymer fiber, while the term "equatorial" is used to describe the direction normal to the fiber axis.
For vector fields (such as wind velocity), the zonal component (or x-coordinate) is denoted as u, while the meridional component (or y-coordinate) is denoted as v.
The term meridional, sometimes abbreviated to "Mer.", was used in historical astronomy to indicate the southern direction on the celestial globe, together with septentrional ("Sep.") for northern, oriental ("Ori.") for eastern and occidental ("Occ.") for western.[1]