Usability

Usability is defined by ISO/IEC/IEEE 25000:2014 SQuaRE -- Guide to SQuaRE as the degree to which a product or system can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use. It further breaks down Usability characteristic to composed of the following sub-characteristics:

Appropriateness Recognizability - Degree to which users can recognize whether a product or system is appropriate for their needs.
Learnability - Degree to which a product or system can be used by specified users to achieve specified goals of learning to use the product or system with effectiveness, efficiency, freedom from risk and satisfaction in a specified context of use.
Operability - Degree to which a product or system has attributes that make it easy to operate and control.
user_error_protection - Degree to which a system protects users against making errors.
user_interface_aesthetics - Degree to which a user interface enables pleasing and satisfying interaction for the user.
Accessibility - Degree to which a product or system can be used by people with the widest range of characteristics and capabilities to achieve a specified goal in a specified context of use.