Merriam-Webster Collegiate Dictionary - preamble

 noun  Etymology: Middle English, from Middle French preambule, from Medieval Latin preambulum, from Late Latin, neuter of praeambulus walking in front of, from Latin prae- + ambulare to walk  Date: 14th century  1. an introductory statement; especially the introductory part of a constitution or statute that usually states the reasons for and intent of the law  2. an introductory fact or circumstance; especially one indicating what is to follow