For Prophylaxis, a particular school of thought in chess pioneered by Tigran Petrosian, please refer to the article on Petrosian.

Prophylaxis refers to any medical or public health procedure whose purpose is to prevent, rather than treat or cure, disease. Vaccines are prophylactic: they are used before illness develop, either being administered to large numbers of people in order to prevent infection, or in some cases (such as the smallpox vaccine) to people who have been exposed to a disease but have not yet become ill.

Antibiotics are sometimes used prophylactically: for example, during the 2001 anthrax attacks scare in the United States, patients who were believed to be exposed were given ciprofloxacin. Similarly, the use of antibiotic ointments on burns and other wounds is prophylactic.

Condoms are sometimes referred to as "prophylactics" because of their use to prevent the transmission of syphilis and other sexually transmitted diseases.

Low molecular weight heparin is used as a prophylaxis in hospital patients, as they are at risk for several forms of thrombosis due to their immobilisation.

Professional cleaning of the teeth is dental prophylaxis.