Forces always occur in pairs. This is related to the fact that a force results from the interaction between two objects. Newton's Third Law says that for every action force there is an equal and opposite reaction force. This means that if one object exerts an action force on a second object, the second object will exert an equal but opposite reaction for on the first object. The action force that is exerted on the second object and the reaction force that the second object exerts back on the first object are known together as action-reaction force pair. Action and reaction force do not cancel each other because they act on different objects.