To bring into a common line or purpose. Alignment is agreement made structural.

How far a thing extends along its longest line. Extent in one direction.

The space kept outside a thing's edge. Room left deliberately unused, so the thing is not crowded.

Short form of pixel — the smallest addressable point of a shown image. A named unit rather than a concept.

A statement of what must or must not be. A rule differs from a description in that breaking it has consequence.

The measured breath between elements — the design token that decides how close things stand. Calm interfaces are made mostly of good spacing.