The visual ranking of elements by importance, expressed through size, weight, color, and position, so the eye knows what to read first.

Example Usage

The page has no hierarchy: the price, the title, and the disclaimer all carry the same visual weight.
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Fig 2.4 Hierarchy

Hierarchy is subtractive: it exists only if most things are visually quiet. If everything is bold, nothing is. The fastest hierarchy fix is rarely making the important thing bigger. It’s making everything else smaller.