<p><strong>Noun</strong></p><ul><li>the state or quality of being active: There was not much activity in the stock market today.</li><li>a specific deed, action, function, or sphere of action: social activities.</li><li>work, especially in elementary grades at school, that involves direct experience by the student rather than textbook study.</li><li>energetic activity; animation; liveliness.</li><li>a use of energy or force; an active movement or operation.</li><li>normal mental or bodily power, function, or process.</li><li>Physical Chemistry: the capacity of a substance to react, corrected for the loss of reactivity due to the interaction of its constituents.</li><li>Physics: the number of atoms of a radioactive substance that disintegrate per unit of time, usually expressed in curies.</li></ul>