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For the purposes of this part of ISO 9241, the following definitions apply: 3.1. usability: The extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use. 3.2. quality of a work system in use: The extent to which specified goals can be achieved with effectiveness, efficiency and satisfaction in a specified work system. Note: The difference between usability and the quality of a work system in use is a matter of focus. When usability is evaluated, the focus is on improving a product while the other components of the work system (user, task, equipment, and environment) are treated as given. When the quality of a work system in use is evaluated any component may be subject to modification or improvement. 3.3. effectiveness: The accuracy and completeness with which users achieve specified goals. 3.4. efficiency: The resources expended in relation to the accuracy and completeness with which users achieve goals. 3.5. satisfaction: The comfort and acceptability of use. 3.6. context of use: The users, goals, tasks, equipment (hardware, software and materials), and the physical and social environments in which a product is used. 3.7. work system: A system, consisting of users, equipment, tasks and a physical and social environment, for the purpose of achieving particular goals. Note: The context of use consists of the goals of the work system and those components of the work system which are treated as given when specifying or measuring usability. 3.8. user: The person who interacts with the product. 3.9. goal: An intended objective. 3.10. task: The activities undertaken to achieve a goal. 3.10. product: The part of the equipment (hardware, software and materials) for which usability is to be specified or evaluated. | 
