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A set of attributes that bear on the effort needed for use, and on the individual assessment of such use, by a stated or implied set of users. (ISO 9126: 1991, 4.3)


  1. `Users' may be interpreted as most directly meaning the users of interactive software. Users may include operators, end users and indirect users who are under the influence or dependent on the use of the software. Usability must address all of the different user environments that the software may affect, which may include preparation for usage and evaluation of results.
  2. Usability defined in this International Standard as a specific set of attributes of software product differs from the definition from an ergonomic point of view, where other characteristics such as efficiency and effectiveness are also seen as constituents of usability. (ISO 9126: 1991, 4.3)