an introduction to a book, typically stating its subject, scope, or aims.
a preliminary explanation:it was an abrupt question, made without even the preface of a greeting
Christian Church the introduction to the central part of the Eucharist, historically forming the first part of the canon or prayer of consecration. In the Western Church it comes between the Sursum Corda and the Sanctus and varies with the season.
provide (a book) with a preface:the book is prefaced by a quotation from William Faulkner
(preface something with/by) introduce or begin (a speech or event) with or by doing something:it is important to preface the debate with a general comment