Breakpoint

The width at which a layout decides to rearrange. A seam chosen on purpose, so the design never tears.

A breakpoint is a confessed limit: the width at which the current arrangement stops serving and the layout, on purpose, becomes another arrangement. Between breakpoints the design flexes; at them, it decides. Each one is a seam sewn where the fabric would otherwise tear.

Chosen on purpose means derived from the content, not the device catalogue: the breakpoint belongs where the line length breaks comfort, where the grid crowds, where the navigation stops fitting, wherever this design strains. Fewer, better-reasoned seams beat many nervous ones; every breakpoint is a second layout to maintain forever.