This book includes studies that employ a variety of research techniques from diverse fields targeting a better understanding of the second language (L2)/foreign language (FL) acquisition process including issues of heritage language (HL) learning. Specifically, the chapters discuss matters such as speech perception and production patterns in a second/foreign language, factors that facilitate second language acquisition, acquisition of heritage languages, teaching of a second/foreign language, and acquisition of second/foreign language grammatical and other structures, among others. The investigation of L2/FL and HLs is of paramount importance for updating the existing theories in the field and maximizing learning outcomes for the sake of effective communication, cultivation of intercultural understanding, career advancement, and personal development. The book is of interest to a wide range of disciplinary audiences, including linguists, psychologists, educators, and social scientists.