What is the difference between radioactive decay and radioactivity?

How can I tell the difference between natural radioactivity and a induced nuclear reaction?

• How can I tell the difference between a natural radioactivity and a induced nuclear reaction when it comes to equations for nuclear reactions.

• Answer:

  when the radio active element decay its self with out any interfere of humane it becomes natural radio activity if the human affect it by any mean (heating electricity hit it with radio active particles such as nitron helium atom ........................................… the reaction began it become radioactive reaction has reactants product and reaction conditions