For example, the aspect ratio of an earlier standard-definition (SD) screen was 4:3, which is a relatively square rectangle. The 4:3 means "4 to 3," or four units wide to three units high.

“The aspect ratio of an image describes the proportional relationship between its width and its height. It is commonly expressed as two numbers separated by a colon, as in 16:9.” – Wikipedia ...

Examples: “A Trip to the Moon” (1902), “The Sting” (1973), and all television until the rise of high definition. Academy Ratio (1932).Aspect ratio: 1.37. To add sound to movies ...