the introductory part of a statute, deed, or the like, stating the reasons and intent of what follows.
a preliminary or introductory fact or circumstance:
His childhood in the slums was a preamble to a life of crime.
(initial capital letter) the introductory statement of the U.S. Constitution, setting forth the general principles of American government and beginning with the words, “We the people of the United States, in order to form a more perfect union. …”.
late 14c., from Old French preambule (13c.) and directly from Medieval Latin preambulum, neuter adjective used as a noun, properly "preliminary," from Late Latin praeambulus "walking before," from Latin prae- "before" (see pre-) + ambulare "to walk" (see amble (v.)).