Perversion is a derogatory term for deviation from the original meaning or doctrine, literally 'turning aside' from what is perceived to be orthodox or normal. A pervert is a person in a state of perversion. By apocopation a 'pervert' becomes a 'perv,' a label proudly carried by many young gay Brits. These terms have two common usages:

• It often refers to "sexual perversion", more neutrally called a paraphilia.

• The term perversion was also used in the pre-Vatican II era by some Roman Catholics to describe the process of converting from Roman Catholicism to Protestantism. Whereas a protestant who joined Roman Catholicism was described as a convert, a Catholic who became a Protestant was called a pervert. The phrase is no longer used by mainstream Catholicism, though a small conservative fringe do on occasion still use it.