Activity (noun)

1. The state or quality of being active; movement, action, operation.
2. Something that a person or group does or has done.

Origin:

From latin activus, from agere ("to d.o")

Examples:

1. The activity of the volcano could be monitored from the space.
2. The children's activity center was filled with laughter and excitement.
3. The company's activity in the field of renewable energy has grown significantly.
4. The activity of the brain during sleep is not yet fully understood.
5. The activity of the enzyme was measured in the lab.