Science refers to any systematic knowledge or practice. In a more restricted sense, science refers to a system of acquiring knowledge based on the scientific method, as well as to the organized body of knowledge gained through such research. This article focuses on the more restricted use of the word.

Fields of science are commonly classified along two major lines:
·        Natural sciences, which study natural phenomena (including biological life), and ·        Social sciences, which study human behavior and societies.

These groupings are empirical sciences, which mean the knowledge must be based on observable phenomena and capable of being experimented for its validity by other researchers working under the same conditions.