Prevention is a group of measures taken to protect a given situation (health, social, economic, environmental, etc.) from damage, an accident or a catastrophe.
Prevention is based on the avoidance of negative events or the reduction of their probability. The preventive aspect is then combined with protection measures.
Protection consists of limiting the negative effects of such events when they take place. This aspect of prevention is based on the concepts of anticipation and prediction, with the implementation of damage reduction measures and early detection systems and alerts.
When a risk is possible but has not yet manifested itself, the precautionary principle is applied, instead of the prevention principle.
This new underground canal is part of a development project to prevent floods in Fordingbridge (United Kingdom). © Clive Perrin, Geograph CC by-sa 2.0