Aspect Ratio
From polycount
Aspect ratio is a number that describes the shape of a rectangular texture, whether it's tall or wide.
To get the aspect ratio, either divide the width by the height, or write it out as width:height. Aspect ratio helps you decide what kinds of changes need to be done to an image to get it to display correctly, like when you have to scale the image.
See also Anisotropic_Filtering.
