Aspect ratio is the ratio of the width of an image or video to its height. It is typically expressed as two numbers separated by a colon, such as 4:3 or 16:9. The aspect ratio of an image or video determines its shape, and different aspect ratios are used for different purposes. For example, the traditional 4:3 aspect ratio, which is commonly used for standard definition television, is well-suited for displaying text and other rectangular content. The more wide-screen 16:9 aspect ratio, on the other hand, is better-suited for displaying video and other content that benefits from a wider field of view. The aspect ratio of an image or video can be changed by cropping or resizing it, but this can result in the loss of some of the original content.