Noah Webster
Activity
ACTIV'ITY, noun The quality of being active; the active faculty; nimbleness; agility; also the habit of diligent and vigorous pursuit of business; as, a man of activity It is applied to persons or things.
Sphere of activity is the whole space in which the virtue, power, or influence of any object, is exerted.
To put in activity a French phrase, for putting in action or employment.