/
ˈprɛfəs/
n.
  - an introduction to a book, typically stating its subject, scope, or aims.
 - Christian Church  the introduction to the central part of the Eucharist.
 
v.
  - provide with a preface.
 - 
(preface something with/by)
 introduce or begin a speech or event with or by doing something.
 
Derivative
- prefatory
  
/ˈprɛfət(ə)ri/
 adj. 
Etymology
ME: via OFr. from med. L. praefatia, alt. of L. praefatio(n-) ‘words spoken beforehand’, from praefari (v.), from prae ‘before’ + fari ‘speak’.