1911 Encyclopædia Britannica/Prolegomenon

PROLEGOMENON (Gr. for “ that which is said beforehand,” προλέγειν, to speak, say before), a preface or introduction to a book, especially a preliminary introductory essay to a learned work, or a treatise which serves as a general survey or introduction to the study of some subject or as a special survey of the subject. The word is more often used in the plural.