A bilingual person, in a broad definition, is one who can communicate in more than one language, be it actively (through speaking, writing, and or signing) or passively (through listening, reading, and or perceiving). More specifically, the terms bilingual and trilingual are used to describe comparable situations in which two or three languages are involved. A generic term for multilingual persons is polyglot. Multilingual speakers have acquired and maintained at least one language during childhood, the so-called first language. The first language (sometimes also referred to as the mother tongue). This new book gathers the latest research from around the globe in this field.