Science (from Latin scientia, meaning “knowledge”) is a systematic enterprise that builds and organizes knowledge in the form of testableexplanations and predictions about the universe. In an older and closely related meaning (found, for example, in Aristotle), “science” refers to the body of reliable knowledge itself, of the type that can be logically and rationally explained (see History and philosophy below). 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 (which is today called “natural science“) 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.