Glossary of Terms

Plain-language definitions for the core vocabulary used across this guide. Skim it now; return whenever a term feels fuzzy.

Product sense

The skill of judging what to build and why it matters to a real person, before and during the build.

User empathy

The ability to see and feel a product from the user's point of view — their goal, confusion, and fear — rather than your own.

Affordance

What an object lets you do; a button affords pressing, a slider affords dragging — the action it physically or visually invites.

Signifier

The visible cue that tells you an affordance exists, like an underline that says "this text is a link" or a handle that says "drag me."

Mental model

The picture in a user's head of how something works; software feels obvious when it matches that picture and confusing when it fights it.

Gulf of execution

The gap between what the user wants to do and figuring out how to do it in the interface ("How do I refund this order?").

Gulf of evaluation

The gap between the system doing something and the user understanding that it happened ("Did my changes actually save?").

Jobs To Be Done (JTBD)

The idea that people "hire" a product to make progress in their lives, so you design for the goal, not the feature.

Cognitive load

The total mental effort a screen demands; the more a user must hold in their head, the harder the product feels.

Hick's Law

The more choices you show, the longer a decision takes — so trim or stage the options.

Miller's Law

People can hold only about seven (give or take two) items in short-term memory at once, so group and chunk information.

Fitts's Law

The bigger and closer a target, the faster and easier it is to hit — make important buttons large and reachable.

Jakob's Law

Users spend most of their time on other products, so they expect yours to work like the ones they already know.

Recognition vs recall

It is far easier to recognize an option that is shown than to recall it from memory — so show choices instead of expecting users to remember them.

Progressive disclosure

Showing only what is needed now and revealing advanced options later, so beginners aren't overwhelmed and experts aren't blocked.

Heuristic evaluation

Reviewing an interface against a short list of usability rules of thumb (like Nielsen's ten) to catch problems without a full study.

Friction

Anything that slows a user down or makes a task feel harder — extra steps, vague labels, forced decisions, or waiting.

Dogfooding

Using your own product the way a real user would, so you feel its rough edges firsthand.

Dark pattern

A design that tricks or pressures users into actions against their interest, like a hidden unsubscribe or a sneaky pre-checked box.

Peak-end rule

People judge an experience mostly by its most intense moment and its ending, not its average — so design strong peaks and clean endings.

Curse of knowledge

Once you know how something works, you can't imagine not knowing — which makes experts blind to what confuses beginners.

Constraint

A deliberate limit that prevents errors by making the wrong action impossible, like greying out "Submit" until a form is valid.

Default

The pre-set choice a user gets without doing anything; a good default is what 90% of people want, so most never have to configure.

Discoverability

How easily a user can find a feature or figure out what's possible without being told.

Feedback

The system's response that confirms an action happened, in plain language ("Saved" not "200 OK").

The Mom Test

A way of interviewing users about their real past behavior, never your idea, so even your mom couldn't accidentally lie to you.

Emotional design

Shaping how a product feels — trust, calm, delight — not just whether it works.