Aspect Ratio
The proportional relationship between the width and height of an image or screen.
Common ratios: 16:9 (widescreen video, modern TVs), 4:3 (older TVs, presentations), 1:1 (square, Instagram), 9:16 (vertical video, phone screens), 21:9 (ultrawide monitors). Maintaining aspect ratio when resizing prevents distortion — stretching or squishing the image. The ratio is found by dividing both dimensions by their greatest common divisor.
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