Learning French from Spanish and Spanish from French provides adult English speakers who have learned either Spanish or French as a second language with the tools to learn the other language as a third language. All human languages have some common elements, but certain languages-because of their shared history-have a great deal in common. French and Spanish are ideal candidates for an approach that highlights their differences in the context of their commonalities. Research in the growing fields of third-language acquisition and multilingualism documents how successful third-language learners intuitively build on the knowledge they acquired while learning a second language. The book takes advantage of the fact that learners with intermediate proficiency in a second language are used to thinking consciously about language, know themselves as language learners, and can capitalize on what they know about one language to understand the other. For students, travelers, and budding multilinguals, the book will accelerate the learning of French or Spanish as a third language.