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.