Aspect ratio is the ratio of _____ to _____.

CONCEPT: Aspect ratio is a proportional relationship that describes the SHAPE of a display or image, independent of its actual size. It is conventionally written as (first quantity) : (second quantity), where the first quantity is the width of the display/image and the second quantity is its height -- for example 16:9 or 4:3.

APPLICATION: Applying this definition to the blanks in the stem: the first blank is filled by width and the second blank by height, so aspect ratio is the ratio of width to height.

CROSS-CHECK: This checks out against common examples -- a 16:9 display has 16 units of width for every 9 units of height, and a 4:3 display has 4 units of width for every 3 units of height. In both cases the first number is width and the second is height, confirming the width-to-height convention.

CONTRAST: Why the other options are wrong:

• Height; width -- reverses the convention's order; width is always stated first, not height.

• Diagonal; height -- confuses the screen SIZE measure (the diagonal, used to state a display's size, e.g. a 24-inch monitor) with one of the two terms of the aspect ratio; the diagonal plays no part in the width:height ratio.

• Height; diagonal -- combines the same diagonal-size confusion with a reversed order.

RESULT: Aspect ratio is the ratio of width to height.