activity

noun (plural activities)

• 1 [mass noun] the condition in which things are happening or being done:there has been a sustained level of activity in the economy
• busy or vigorous action or movement:the room was a hive of activity

• 2 (usually activities) a thing that a person or group does or has done:the firm’s marketing activities
• a recreational pursuit or pastime:a range of sporting activities

• 3 Chemistry a thermodynamic quantity representing the effective concentration of a particular component in a solution or other system, equal to its concentration multiplied by an activity coefficient.