Glossary
A design system is a set of reusable components and the decisions behind them (colour, type, spacing, states), recorded so that the same problem is not re-solved differently on every page.
The half that makes a system durable is the recorded reasoning: which colour pairings are permitted and why, what a heading level means, when a card is appropriate. Without that, teams reuse the components and still produce inconsistent pages.
On a small site a design system is overhead. Across a large site maintained by several people over years, it is what prevents the slow divergence where each new page is slightly different from the last.
Contrast ratios asserted in a check that fails the build are a system; contrast ratios listed in a document are a suggestion.
Rarely at first. It pays off where several people maintain a site over years, or where one brand spans several products. On a single small site it is overhead that slows the first release.
Enforcement. Constraints checked automatically (contrast, spacing, type scale) hold. Constraints written in a document drift within months of the people who wrote them moving on.
A design system is a set of reusable components and the decisions behind them (colour, type, spacing, states), recorded so that the same problem is not re-solved differently on every page.
