Just Say Nu By Michael Wex St. Martin's Press 320 pages; $23.95 So you enjoyed Michael Wex's Born to Kvetch, a North American introduction to Yiddish which we reviewed last year? Even if you have no social connection with the haredi Ashkenazic community, you will probably also enjoy Just Say Nu - Yiddish for Every Occasion, a Wex spinoff again published in New York by St. Martin's Press. But caveat emptor: To get something out of this guide you must be at least familiar with the sounds and popular pronunciations of Yiddish. The reason? Yiddish is written in Hebrew characters, but not in this guide for Jews and goyim alike. The transliterations are only an approximation of the world's funniest spoken language. The Yiddisher Visnshaftlikher Institute (Yivo) has developed the standard system used in American universities and libraries. But almost nobody speaks it. Wex has chosen his own system, based on his personal mameloschen, Polish Yiddish. He does provide a guide to pronunciation and a useful dictionary of all terms employed. He acknowledges a major debt to two dictionaries still in print, Alexander Harkavy's Yiddish-English-Hebrew Dictionary (Yale, 1928); and Uriel Weinreich's Modern English-Yiddish Yiddish-English Dictionary (Schocken Books, 1968). Wex is a humorist and he opens this volume with a very funny dirty story which gives the book its title. In fact the book is a guide to sexual and genital terms and also groping, French-kissing and shtupping; there is even a sly drawing on the cover in which a fetching young lady pats a guy dortn and says "nice tukhes!" Yiddish is mainly medieval German flavored with key Hebrew sources. If you happen to have a fair knowledge of both German and Hebrew you can trace the origins of both in a single expression. During the Enlightenment, Yiddish emerged as a literary phenomenon, but this book has little to do with literature. It's nearer Yiddish theater and it's a delight.