activity
noun(ac-tiv-i-ty)
an organic process that takes place in the body
Synonyms: bodily function, bodily process, body process, 
Examples:
Respiratory activity. 
activity
noun(ac-tiv-i-ty)
the state of being active
Examples:
His sphere of activity. 
activity
noun(ac-tiv-i-ty)
the trait of being active; moving or acting rapidly and energetically
Examples:
The level of activity declines with age. 
activity
noun(ac-tiv-i-ty)
a process existing in or produced by nature (rather than by the intent of human beings)
Synonyms: action, natural action, natural process, 
 Examples:
Volcanic activity. 
activity
noun(ac-tiv-i-ty)
any specific behavior
Examples:
They avoided all recreational activity. 
activity
noun(ac-tiv-i-ty)
(chemistry) the capacity of a substance to take part in a chemical reaction
Examples:
Catalytic activity.