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Usability glossary


Terms and definitions used in the User Experience profession.

7 plus or minus 2

The number of items that can be held in short-term memory or that can be the focus of attention, as stated by George A. Miller in his 1956 paper. The number applies only to retention and recall of information, and not to recognition. "The Magic Number Seven, Plus or Minus Two: Some Limits on our Capacity for Processing Information" (The Psychological Review, 1956, vol. 63, pp. 81-97).<

See also: Chunking, Hick's law (Hick-Hyman law)

The attributes and characteristics of a system that allow people with limited vision, hearing, dexterity, cognition or physical mobility to interact effectively with the system. Standards and guidelines are available, and standards may be legally enforced in some markets. Accessibility aids, such as screen readers, may be added to a system to allow people with disabilities to use those systems.<

Synonyms: ARIA, Section 508, WAI WCAG
Affinity Diagramming

Affinity diagramming is a participatory method where concepts written on cards are sorted into related groups and sub-groups. The original intent of affinity diagramming was to help diagnose complicated problems by organizing qualitative data to reveal themes associated with the problems.<

Synonyms: Mind mapping

The properties of an object that inform people how the object could be used. The term 'perceived affordance' applies when the object properties are perceived in a way that differs from the real-world, physical properties, especially when the usage of the object depends on perceived rather than real-world properties.<


Braindrawing is a type of visual brainstorming in which a group of participants sketch ideas for designs, icons, screen layouts, or other visual concepts.

See also: Brainstorming

A method for generating ideas, intended to inspire the free-flowing sharing of thoughts of an individual or a group of people, typically while withholding criticism in order to promote uninhibited thinking.

See also: Braindrawing, Brainwriting, Metaphor Brainstorming

Brainwriting is a method for quickly generating ideas by asking participants to write their ideas on paper (or online) rather than announcing them in traditional group brainstorming sessions. Brainwriting has the advantage of parallel idea generation. In traditional group brainstorming, only one idea can be presented at a time (a serial process). In brainwriting, you can have the entire group writing ideas at the same time.

See also: Brainstorming
Card Sorting

A method for organizing information that involves sorting a series of cards into groups that make sense to the participants. Each card represents a single term, function or object. Card sorting helps to reveal users' mental models, or patterns that the end users would expect to find.

Case Study

A way of learning about a complex instance through extensive description and analysis. The case study articulates why the instance occurred as it did by exploring the factors contributing to its success or failure, and what one might consider in similar situations.


A checklist is a predefined set of guidelines, tasks, or other items against which products, processes, behaviors, user interface components, or something else, are compared.


The human ability to group information into related small sets, which can then be stored in short-term memory. By keeping information in smaller pieces, the functional storage capacity of the brain is increased. Information is often presented in a chunked format to facilitate human memory, for example North American phone numbers are often grouped into the xxx-xxx-xxxx pattern. Familiarly with the information and/or rehearsal of it increases the person's ability to remember the information.

See also: 7 plus or minus 2
Claims Analysis

Claims analysis is a technique for examining the positive and negative consequences of design features that are described in current or future scenarios of use. A "claim" is a statement of the consequences of a specific design feature or artifact on users and other stakeholders.

Cognitive Walkthrough

The cognitive walkthrough is a usability evaluation method in which one or more evaluators work through a series of tasks and ask a set of questions from the perspective of the user.

See also: Heuristic Walkthrough, Pluralistic Usability Walkthrough
Competitor Analysis

A method for identifying the strengths and weaknesses of competing products or services before starting work on prototypes.


The characteristics of a graphic element that enable the audience to differentiate the element from its surrounding environment. Conspicuity is achieved when each element can easily be distinguished separately by the user.

Context of Use Analysis

Collecting and analyzing detailed information about the intended users, their tasks, and the technical and environmental constraints. The data for a context of use analysis can be gathered using interviews, workshops, surveys, site visits, artifact analysis, focus groups, observational studies, and contextual inquiry.

Contextual Inquiry

A semi-structured field interviewing method based on a set of principles that allow it to be molded to different situations. This technique is generally used at the beginning of the design process and is good for getting rich information, but can be complex and time consuming.

See also: Ethnography, Field Study
Critical Incident Technique (CIT)

A method of gathering facts (incidents) from domain experts or less experienced users of the existing system to gain knowledge of how to improve the performance of the individuals involved. CIT is used to look for the cause of human-system (or product) problems to minimize loss to person, property, money or data.

Cultural Probe

Cultural probes are sets of simple artifacts (such as maps, postcards, cameras, or diaries) that are given to users for them to record specific events, feelings or interactions in their usual environment, in order to get to know them and their culture better. Cultural probes are used to uncover aspects of culture and human interaction like emotions, values, connections, and trust.

See also: Diary Study, Photo Study

The shared set of habits, customs, knowledge, beliefs, language, and behaviors that set one group of people apart from others. This grouping may range from very large to very small groups (such as an office or a business). Culture is invisible to people who are part of it, and often incomprehensible to people who are encountering a specific culture for the first time. The risk of culture for usability is that culture is a deep source of unstated assumptions. These assumptions need to be identified and stated explicitly before they can be incorporated into a usable design.

See also: Ethnography
Diary Study

A diary study requires users, or observers of users, to keep track of activities or events in some form of diary or log for a particular period of time.

See also: Cultural Probe
Easy to Learn

The aspect of usability that focuses on facilitating the users learning of an interface, with minimum time and effort spent in the learning phase.


The attribute of usability that focuses on task completion, guiding the user through all parts of the task and ensuring that the task is properly completed.


The attribute of usability that focuses on being able to accomplish a task in minimum time with a minimum of effort.


The attribute of usability that focuses on capturing and holding the user's attention and interest.


The process of gathering information about users and tasks directly from users in their normal work, home or leisure environment. Traditional more on Ethnography)">ethnography focuses on long-term studies spanning weeks, months, or even years. Information may be collected through participant observation, interviews, audio or video recording, observer logs, artifact collection, diaries and photographs. (more on Ethnography<)

See also: Contextual Inquiry, Culture

A person that works with a person or group to lead a discussion or activity in order to extract feedback and information. A facilitator's goals might include developing an understanding of a situation or objective, help achieve consensus, understand the differences or obstacles that stand in the way of the end goals, and clarify various view points. Key skills for a facilitator include timekeeping, application of behavioral tools to help achieve the desired test or activity goals, listening, asking questions, suggesting alternatives, and moving the test or activity forward and keeping records. A facilitator might preside over various forms of user research.

See also: Moderator
Field Study

A field study is a general method for collecting data about users, user needs, and product requirements that involves observation and interviewing. Data are collected about task flows, inefficiencies, and the organizational and physical environments of users.

See also: Contextual Inquiry
Fishbone Diagram

A graphic that is created to identify cause-and-effect relationships among factors in a given situation. It is made up of a 'head' which states a problem and bones along the spine which represent factors and categories of factors.

Synonyms: Cause-and-effect diagram, Fault tree diagram, Ishikawa diagram, Root cause analysis
Fitts' Law

The further away a target is, and the smaller its size, the longer it will take for a user to reach it. The time required to move from a starting point to within the confines of a target area is dependent on a logarithmic relationship between the distance from the point to the target area and the size of the target.

Focus Group

A focus group is a focused discussion where a moderator leads a group of participants through a set of questions on a particular topic. Focus groups are often used in the early stages of product planning and requirements gathering to obtain feedback about users, products, concepts, prototypes, tasks, strategies, and environments.

See also: Moderator
Formative Evaluation

Formative evaluation is a type of usability evaluation that helps to 'form' the design for a product or service. Formative evaluations involve evaluating a product or service during development, often iteratively, with the goal of detecting and eliminating usability problems.

Free Listing

Free listing is a technique for gathering data about a specific domain or topic by asking people to list all the items they can think of that relate to the topic. It can be used to gather data in large group settings or in one-on-one interviews.

Function Allocation

Function allocation is a classic human factors method for deciding whether a particular function will be accomplished by a person, technology (hardware or software) or some mix of person and technology. To do this, the investigator considers error rates, fatigue, costs, hazards, technological feasibility, human values, ethical issues, and the desire of people to perform the function.

Gestalt Principles

Humans visually perceive items not in isolation, but as part of a larger whole. These principles include humans tendencies towards similarity, proximity, continuity, and closure.

Graceful Degradation

Systems should be designed so that when features that take advantage of new technologies are disabled, the content maintains effectiveness for the users. For example, older Web browsers and browsers which allow users to disable features will display page content in a simplified format.


A usability guideline for evaluating a user interface, which can be used to identify design problems. Usability heuristics often need to be adjusted depending on the interface and the technology used. There are lists of heuristics that have been compiled by various people and organizations that are commonly used for this method.

Heuristic Evaluation

A usability evaluation method in which one or more reviewers, preferably experts, compare a software, documentation, or hardware product to a list of design principles (commonly referred to as heuristics) and identify where the product does not follow those principles.

Heuristic Walkthrough

A type of inspection that combines aspects of heuristic evaluation, the cognitive walkthrough, and the pluralistic usability walkthrough.

See also: Cognitive Walkthrough
Hick's law (Hick-Hyman law)

The time it takes to make a decision increases proportionally to the number and complexity of choices. Hick's law is the appropriate model in choosing an alternative from a menu or navigation bar for decision times, rather than Miller's "magic number" of seven plus or minus two.

See also: 7 plus or minus 2
Human Factors

The multidisciplinary study of human biological, physical, psychological, and social characteristics in relation to environments, objects and services. The practice of human factors applies to the design, operation, and evaluation of systems to ensure that that they are safe, efficient, comfortable and aesthetically pleasing to humans.

Human-Computer Interaction (HCI)

A discipline concerned with the design,evaluation and implementation of interactive computing systems for human use and with the study of major phenomena surrounding them. (from HCI Bibliography,

Industrial Design

An applied art focusing on the aesthetics, usability, ergonomics, and production of physical products, such as automobiles, appliances and consumer electronics. Industrial designers may specify the overall shape, interactive properties, colors, texture, and sounds of an object, as well aspects of the manufacturing process.

Information Architecture (IA)

The process of organizing information including the structure, design, layout and navigation in a way that is easy for people to find, understand and manage the information.

Interaction Design

The discipline of Interaction Design (IxD) defines the structure and behavior of interactive systems. Interaction Designers strive to create meaningful relationships between people and the products and services that they use, from computers to mobile devices to appliances and beyond. (From the Interaction Design Association web site:

See also: User-Centered Design (UCD)

A view or presentation of an object, service, or environment that a person (or group) interacts with, and the capabilities that provide for interaction across the interface.


The process of developing a system whose core design works in multiple languages and in the cultural contexts of different locales, without having to be redesigned for each locale.

See also: Localization
Iterative Design

Design methodology involving repeated cycles of design, evaluation, and analysis. Refinements are made for the next cycle based on the analysis and feedback.


Part of the GOMS family of predictive models, the Keystroke-Level Model GOMS (KLM-GOMS) is a quantitative modeling tool for predicting how long it will take expert users to complete a specific task with no errors.


A measure of the degree to which a user interface can be learned; an attribute of a usable system. The ease of learning the functionality of a system and gaining proficiency to complete basic and necessary tasks. Factors affecting this measure include the amount of time, training, and support required for the user to learn the system.

See also: Readability
Likert Scale

A response range for a type of survey question in which a person is asked to agree or disagree with a statement. The scale typically runs from 1 ("strongly disagree") to 5 or 7 ("strongly agree"). With a Likert scale, neither the numerical scores nor the intervals between score values have any intrinsic meaning.<

See also: Rating Scales

Customizing an internationalized product for a specific market. When a product has been properly internationalized, the visual design can be preserved when it is adapted for a particular audience, even while the language is translated, formats converted and layout adjusted.

See also: Internationalization
Longitudinal Study

A study that captures data over a period of time (days, week, months or years) to understand the long-term effects of changes in products, processes or environment.

Metaphor Brainstorming

Metaphor brainstorming is a method for generating metaphors and extracting aspects of those metaphors that can be applied to the design of hardware, software, processes, and services. SEE Brainstorming. Read more about Metaphor Brainstorming.

See also: Brainstorming

A person that works with a group to regulate, but not lead, a discussion. Whereas a facilitator might take charge of a discussion to shepherd it in a specific direction, a moderator remains passive, without explicitly leading the process or driving a desired outcome. A moderator takes the lead from the participants, listening and intervening only when necessary to encourage further discussion or ask for clarity for other participants or audiences. SEE Facilitator.

See also: Facilitator, Focus Group
Paper Prototyping

A study conducted on a paper version of a design to get feedback early on in the design process.

See also: Wireframe Synonyms: Low-fidelity prototype
Parallel Design

A method where several design groups produce alternative designs in parallel, with the objective of incorporating the best aspects of each design in the final solution.

Participatory Design

A process that involves developers, business representatives, and users working together to design a solution. It actively involves users in the design process to help ensure that the product designed meets their needs and is usable in the process.


Fictional person created to model and describe the goals, needs, and characteristics of a specific type or group of users. Does not describe a real, individual user nor an average user. Often includes made-up personal details to make the fictional person more "real".

Phone Interview

A semi-structured or structured interview that is conducted over a phone or Internet audio line. Phone interviews can supplement other HCI methods and allow HCI specialists to follow users over an extended time.

Photo Study

Users take photos to highlight important aspects of their lives and context. The photos are assembled into collages and studied to highlight opportunities for new technologies and barriers to their acceptance.

See also: Cultural Probe
Pluralistic Usability Walkthrough

A usability test method employed to generate early design evaluation by assigning a group of users a series of paper-based tasks that represent the proposed product interface and including participation from developers of that interface.

See also: Cognitive Walkthrough

A lightweight initial design of an interface or product, used to capture initial concepts and layouts to gather feedback from users, as well as project participants and stakeholders.

Rapid Prototyping

The creation of low-cost representations of the user interface to a system as a method of brainstorming, creating, testing and communicating ideas about the system being developed.

See also: Wireframe
Rating Scales

A series of response options to research questions, representing degrees of a particular characteristic. The options are specifically ordered with sequential values (known as "ordinal") and have little overlap between neighboring options.

See also: Likert Scale

A measure of the degree to which an interface can be easily and accurately read; an attribute of a usable system. The level of difficulty of vocabulary and the complexity of sentences in a written text usually ranked by the age or grade level required for a person to readily understand the text. People can more easily perceive a message correctly when the vocabulary and sentences are simple and clear.

See also: Learnability Synonyms: Plain language

A story which has the key elements of a realistic situation when the user would interact with the system being designed or evaluated. The scenario includes consideration of the user's goals, tasks and interaction. Scenarios can be created for user groups, workflows or tasks to explore, understand and test the different types of needs and goals.

Site Map

A representation of the information that can be found on a Website or of a system. When presented as content on a Website it is typically organized in a hierarchical listing. Alternatively, the same information can be represented with boxes and arrows that visually show the hierarchy of the interface.


A technique for illustrating an interaction between a person and a product (or multiple people and multiple products) in narrative format, which includes a series of drawings, sketches, or pictures and sometimes words that tell a story. Read more about the Storyboard method.


The procedures that include goals, steps, skills, start state, inputs, end state, and outputs required to accomplish an activity. They can be organized into larger tasks such as driving to work and sub-tasks such as opening the car door.


A scheme for classifying a body of knowledge and defining the relationships among the pieces. Sometimes referred to as a controlled vocabulary, a taxonomy is often used to classify content to aid in the creation of information architecture. SEE Information Architecture.

Testing (Usability)

The process of validating that a system meets pre-specified usability objectives. These objectives should be task-based, and should tie directly to product requirements, including results from analytic tools such as personas, scenarios, and task analysis. Testing may validate a number of objective and subjective characteristics, including task completion, time on task, error rates, and user satisfaction. Testing may be formal or informal, may be local (with testers physically present at same location as users) or remote, and may result in qualitative or quantitative data. Testing may occur at any point in the development cycle, from early analysis through product delivery and beyond. Testing may be based on paper designs, models, or display mock-ups, as well as on products in development and completed products.

See also: Usability Evaluation, Wizard of Oz
Think-aloud Protocol

A direct observation method of user testing that involves asking users to think out loud as they are performing a task. Users are asked to say whatever they are looking at, thinking, doing, and feeling at each moment. This method is especially helpful for determining users' expectations and identifying what aspects of a system are confusing.


Usability is the degree to which something - software, hardware or anything else - is easy to use and a good fit for the people who use it.

Usability Engineering

The disciplined application of usability practices to assess the needs and abilities of users, in conjunction with the business requirements, practices, and processes of an organization. These are combined to develop an effective user experience, and to integrate that experience into a product or service. Usability engineering also encompasses the business and interpersonal skills to work effectively with the business and development organizations to integrate usability practices and goals within the overall development, marketing, support, training, and quality assurance processes of the product group.

Usability Evaluation

Assessing the usability of a product with the purpose of identifying usability problems and/or obtaining usability measures. The purpose of evaluation can be to improve the usability of the product as part of design/development (formative evaluation), or to assess the extent to which usability objectives have been achieved (summative evaluation).

See also: Testing (Usability), Wizard of Oz
User Experience (UE)

Every aspect of the user's interaction with a product, service, or company that make up the user's perceptions of the whole. User experience design as a discipline is concerned with all the elements that together make up that interface, including layout, visual design, text, brand, sound, and interaction. UE works to coordinate these elements to allow for the best possible interaction by users.

User-Centered Design (UCD)

An approach or philosophy that emphasizes early and continuous involvement of users in the design and evaluation process.

See also: Interaction Design

How people orient themselves and navigate in a built environment, both physical and virtual.


Rough outline of navigation and content elements that make up a user interface. Typically visual design and precise layout are not addressed.

See also: Paper Prototyping, Rapid Prototyping
Wizard of Oz

A user-based evaluation of unimplemented technology where, generally unknown to the user, a human or team is simulating some or all the responses of the system.

See also: Testing (Usability), Usability Evaluation
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