Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe. In an older and closely related meaning, "science" refers to the body of reliable knowledge itself, of the type that can be logically and rationally explained. Since classical antiquity science as a type of knowledge was closely linked to philosophy.
In the early modern era the words "science" and "philosophy" were sometimes used interchangeably in the English language. By the 17th century, natural philosophy was considered a separate branch of philosophy. However, "science" continued to be used in a broad sense denoting reliable knowledge about a topic, in the same way it is still used in modern terms such as library science or political science.