Hierarchy created by pairing clearly different font weights, often at the same size, instead of changing the type size.

Example Usage

Keep the row height fixed: the label is regular, the value is semibold. Weight contrast does the work.
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Fig 3.7 Weight contrast

Weight contrast is the quietest hierarchy tool: it ranks information without disturbing the layout the way size changes do. The trap is adjacent weights: regular against medium reads as a rendering error, not a decision. Skip at least one weight; contrast must be unmistakable to count as contrast.