Nudism is the practice — and the belief — of going without clothes on purpose, because you think it is natural and healthy. The line people often hear is about someone who enjoys that; that someone is a nudist. Nudism itself names the way of life, not the person. It is not the same as being caught undressed by accident, and it is not the same as a sexy show. People who follow it often meet in private clubs, beaches, or camps where everyone has agreed to the same rule. The word is a bit formal and a bit old; some speakers now say naturism for the same idea, especially in Europe. In news and school talk, nudism is the movement. Though actually, outsiders sometimes use the word with a raised eyebrow, so the tone around it is not always calm.

裸體運動；天體主義（指做法與信念，不是某一個人才叫 nudism）