Contrast
The difference in luminance between two colors, usually text and its background — expressed as a ratio from 1:1 (identical) to 21:1 (black on white).
Example usage
“That label gray fails contrast on the tinted card — 2.8:1 where body text needs 4.5:1.”
Editor’s note
Contrast is the only word in this category with a pass/fail grade: WCAG asks 4.5:1 for body text and 3:1 for large type, and no amount of taste overrules it. The fashionable failure is the whisper-gray caption on a white card — elegant in a Dribbble shot, gone on a sunlit train. Luminance isn’t the only lever either; size and weight contrast can rescue a pair of colors that the ratio alone would condemn.