The document defines usability and explains how to identify the information which is necessary to take into account when specifying or evaluating usability in terms of measures of user performance and satisfaction. Guidance is given on how to describe the context of use of the product (hardware, software or service) and the required measures of usability in an explicit way. The guidance is given in the form of general principles and techniques, rather than in the form of requirements to use specific methods. The guidance can be used in procurement, design, development, evaluation and communication of information about usability. The design of the usability should influence the ergonomic aims positively, e. g. to reduce negative effects of usability for personal health, safety and performance.