User experience   ( UX ) refers to a person's emotions and attitudes about using a particular   product ,   system   or service. User experience includes the practical, experiential, affective, meaningful and valuable aspects of human–computer interaction and product ownership. Additionally, it includes a person’s perceptions of system aspects such as utility, ease of use and efficiency. User experience may be considered subjective in nature to the degree that it is about individual perception and thought with respect to the system. User experience is dynamic as it is constantly modified over time due to changing usage circumstances and changes to individual systems as well as the wider usage context in which they can be found. Definitions The international standard on  ergonomics of human system interaction , ISO 9241-210, defines user experience as "a person's perceptions and responses that result from the ...