The present text is a re-edition of Volume I of Formal Grammars in Linguistics and Psycholinguistics, a three-volume work published in 1974. This volume is an entirely self-contained introduction to the theory of formal grammars and automata, which hasn’t lost any of its relevance. Of course, major new developments have seen the light since this introduction was first published, but it still provides the indispensible basic notions from which later work proceeded. The author’s reasons for writing this text are still relevant: an introduction that does not suppose an acquaintance with sophisticated mathematical theories and methods, that is intended specifically for linguists and psycholinguists (thus including such topics as learnability and probabilistic grammars), and that provides students of language with a reference text for the basic notions in the theory of formal grammars and automata, as they keep being referred to in linguistic and psycholinguistic publications; the subject index of this introduction can be used to find definitions of a wide range of technical terms. An appendix has been added with further references to some of the core new developments since this book originally appeared.