Prolegomenous is an uncommon word that refers to something that introduces or serves as a preface. There are various synonyms for prolegomenous, including introductory, preliminary, prefatory, initial, prelim, primary, opening, beginning, preparatory, and lead-in. Each of these words can be used to describe something that initiates or leads to something else. For example, an introductory chapter in a book serves as a prolegomenous section to the rest of the book, while a preparatory phase may be considered prolegomenous to an experiment or project. Using synonyms for prolegomenous can help to spice up your writing and convey the same idea with a different flavour.