Activity
Activity may refer to:

Action (philosophy), in general
Human activity: human behavior, in sociology behavior may refer to all basic human actions, economics may study human economic activities and along with cybernetics and psychology may study their modulation
Recreation, or activities of leisure
The Aristotelian concept of energeia, Latinized as actus
Activity (UML), a major task in Unified Modeling Language
Activity, the rate of catalytic activity, such as enzyme activity (enzyme assay), in physical chemistry and enzymology
Thermodynamic activity, the effective concentration of a solute for the purposes of  mass action
Activity (project management)
Activity, the number of radioactive decays per second
Activity (software engineering)
Activity (soil mechanics)
HMS Activity (D94), an aircraft carrier of the Royal Navy
"Activity", a song by Way Out West from Intensify
Cultural activities, activities referred to culture.

See also
Activity theory, a learning theory in education
Social activity (disambiguation), several concepts in the social sciences
Activiti (software), an open source Business Process Management platform
Active (disambiguation)