The volume is a collection of original articles that present new research on first and second language acquisition from the perspective of current generative linguistics, using a detailed case study of Portuguese as a first, second and third language. The book focuses on studies exploring both empirical/experimental and theoretical aspects of the acquisition of syntax and its interfaces with morphology, with semantics/pragmatics, and language change. The volume includes chapters on the child and adult acquisition of European and Brazilian Portuguese, and several chapters that also compare and contrast the two varieties from these different perspectives.