(pref′is) noun
1. A brief explanation or address to the reader at the beginning of a book or other publication.
2. Any introductory speech, writing, etc.
—v.t. ·aced, ·ac·ing
1. To introduce or furnish with a preface.
2. To serve as a preface for. [<OF <L praefatio <praefatus, pp. of praefari utter beforehand, premise <prae- before + fari speak]

(pref′is) noun Eccl.
1. The prayer of thanksgiving, ending with the Sanctus, which introduces the canon of the mass.
2. The corresponding section in other eucharistic liturgies.