Prevention (noun)

1. The act of preventing something from happening.
2. The act of stopping something from happening before it starts.
3. The action of taking measures to stop something bad happening.

Origin:

From old french, from latin praeventio, from praevenire ("to anticipate, forestall"), from prae ("before") + venire ("to come").

Examples:

1. The prevention of accidents is the responsibility of every employee.
2. The best treatment for a disease is often prevention.
3. Wearing sunscreen is a prevention against skin cancer.
4. The city has implemented several prevention measures to reduce air pollution.
5. The government has launched a prevention campaign to stop the spread of the virus.