Knowing which words to use and how to use them is key to communicating accurately and effectively. That’s why more than one million people have used this book to improve their vocabularies.To find out which words you absolutely need to know, The Princeton Review researched the vocabularies of educated adults by analyzing major newspapers and books and focusing on the words that people misunderstand or misuse. We also examined the SAT and other standardized tests to determine which words are tested most frequently..