prolegomenon

from WordNet (r) 3.0 (2006)

prolegomenon
    n 1: a preliminary discussion inserted at the beginning of a
         book or treatise

from The Collaborative International Dictionary of English v.0.48

Prolegomenon \Prol`e*gom"e*non\, n.; pl. {Prolegomena}. [ NL.,
   fr. Gr. ?, properly neut. pass. p. pr. of ? to say
   beforehand; ? before + ? to say.]
   A preliminary remark or observation; an introductory
   discourse prefixed to a book or treatise. --D. Stokes (1659).
   Sir W. Scott.
   [1913 Webster]