Aspect ratio
From The Glossary of Digital Photography
The ratio between the width (long dimension) and height (short dimension) of a photographic sensor or image. In digital cameras, typical aspect ratios are 3:2 (the same as 35mm film), 4:3, or 16:9. Common print sizes of 3 1/2 inches by 5 inches and 4 inches by 6 inches are in a ratio of 3:2 because they are often made from digital camera images. Larger and more traditional print sizes, such as 8 inches by 10 inches, are a different aspect ratio and require cropping
when made from digital images.
