Learn in the textbookBasic Principles of Design and Organizing Information
DefinitionProximity (近接) is the principle of placing closely related elements near each other and leaving space between unrelated ones, so that the grouping of information is visible.
ExplanationReaders see things that sit close together as one group. Tighten the gap between a heading and its text and leave wider space before the next item, and the break comes across even without a border. If everything is spaced evenly, it becomes unclear where one set ends and the next begins.
AnalogyPeople chatting in a circle stand close together and a little apart from the next circle, so even from a distance you can tell who is with whom.
Memory hookThe word comes from Latin proximus, "nearest": distance itself is what marks a group.