The Law of Ancient Rome is a set of laws that were used in the Roman Republic and later the Roman Empire. The term 'Lex' is derived from the Latin word for law, and it was used to refer to the body of Roman law. This body of law was based on the Twelve Tables, which were the first written code of Roman law. It was later expanded and modified by the Roman Senate and other legal authorities. The Law of Ancient Rome was influential in the development of modern legal systems around the world.