Language wears many hats, but its most important job is to help us name or describe what's in the world. Words define us, our actions, even our existence. And just when you think that you have all the words you need, you discover new ones, hear new uses for old ones or see them mutate right before your eyes-a neologism is born.

Those neologisms are actually one of the best ways of keeping tabs on the way our world and culture are changing. One of the people who's been keeping tabs is Paul McFedries, the president of Logophilia Limited (logophilia is Greek for "the love of words"). His scorecard is Word Spy, a daily newsletter that has been reporting from the neological frontier since 1998 and that has more than 100,000 visitors a month and more than 12 million page views. In Word Spy, McFedries demonstrates how new words both reflect and illuminate not only the subcultures that coin them but also the larger culture in which these groups exist. Neologisms give us insight into the way things are even as they act as linguistic harbingers of what's to come. Each chapter of Word Spy is a cultural snapshot, a slice of the zeitgeist that focuses on a specific idea or sociological phenomenon, with an emphasis on the words and phrases that it has generated. These snapshots cover various aspects of modern life, including relationships, business, technology, war, aging, multiculturalism, and even fast food, all the while introducing us to hybrid words: If your kids can't seem to get away from their computers, they may be addicted to "fritterware" (time-wasting game software). If you're a new mother with a passion for petitioning, you may be a "lactivist" (breast-feeding activist). And if you keep finding yourself staying way later at the office than you ever imagined, you may be suffering from "presenteeism."

Word Spy is an exciting and informative travelogue through the evolving landscape of our language and, consequently, the cultures and subcultures that continually mold and shape not just the language but all of us who speak it.