I’ve recently begun reading A Theology for the Church, a book on systematic theology edited by Daniel L. Akin. Theologians often have (and use) a broad vocabulary, so I expect this book to be a treasure trove of new words. For instance, in the first few pages I found these.
While some of these words aren’t technically new to me, I was unsure of the precise definition of some. The meaning of other words eluded me entirely. For instance:
: prefatory remarks; specifically a formal essay or critical discussion serving to introduce and interpret an extended work 
The title of the first chapter is “Prolegomena: Introduction to the Task of Theology”. Thus, this new word appears to be used entirely correctly!
1. Merriam-Webster OnLine