Match Between System and the Real World
Use words, controls, and patterns that make sense to the people using the product.
The best interface speaks in terms people already understand.
A button labeled "Submit Form Payload" may make sense to a developer. To everyone else, "Send application" is clearer. Good interfaces use familiar words, expected order, and controls that behave the way people already understand.
Origin
Nielsen made this the second heuristic in his 1994 revision. It asks designers to use familiar language, follow real-world conventions, and present information in a natural order. Anna Kaley expanded on it for NN/g in 2018.
Use the words your audience uses. Research labels with real users instead of assuming your team's language will make sense outside the company.
Arrange information in the order people expect to encounter it. Put instructions and warnings beside the step where they matter.
Let controls reflect their outcome. A volume-up control belongs above volume-down because the position matches the change.
Use familiar conventions, but test them with your audience. A symbol or phrase that feels obvious to one group may confuse another.
Digital systems
Compass apps
A compass app can reuse the dial, needle, and cardinal directions of a physical compass. People who know the real object can read the digital version without learning a different set of controls.
Physical signals
Stove control mapping
Stove controls are easier to understand when their layout matches the burners. A two-by-two arrangement makes each relationship visible. A straight row of knobs leaves labels to do the mapping work.
Internal terms, unfamiliar icons, and unexpected ordering force people to translate before they can act. The product may follow its own logic while still feeling confusing to everyone outside the team.
Write in familiar language, follow established conventions, and mirror the sequence of the real task. Test those choices with the people who will use the product.