The study of nature and natural phenomena. Application of the term did not begin with any formal definition; rather the various disciplines arose independently, each in response to some particular need. It was then observed that certain of these disciplines had enough traits in common to justify classifying them together as one of the sciences. Usage is not, however, always unanimous as to whether some disciplines should be called sciences, and there is often lively controversy as to the propriety of speaking of the social or historical sciences.