an organic process that takes place in the body
"respiratory activity"
(chemistry) the capacity of a substance to take part in a chemical reaction
"catalytic activity"
a process existing in or produced by nature (rather than by the intent of human beings)
"the action of natural forces"
"volcanic activity"
the trait of being active; moving or acting rapidly and energetically
"the level of activity declines with age"
The state or quality of being active; activeness.
"The new gym equipment is designed specifically to maximize physical activity during your workout routine."
In plain English: An activity is something you do for fun, work, or exercise.
"She decided to take up yoga as a new activity to stay fit."
Usage: Use activity to refer to a specific action, task, or event that someone does, rather than the general concept of being energetic. It often describes hobbies, sports, or work duties in everyday conversation.
The word activity comes from the Middle French activité, which was borrowed from the Latin activitas. It entered English as a noun formed by adding the suffix -ity to the root active.