Law often appears in technical language, the meaning of which is not always apparent to the uninitiated. In this chapter, the author focuses on some of the crucial concepts that are often presumed in law. They look at some of the most basic concepts of law and give the students some good working definitions. The precise significance of such ‘rules’ and the way in which they are ‘recognised’ remains the subject of much dispute. Positivists argue that law properly understood is restricted to rules laid down in advance by those who have ultimate power in a political community. The former thus includes constitutional and administrative law, while the latter includes torts, contracts, property and the like.