Programming Languages: Concepts and Implementation is a textbook on the fundamental principles of programming languages through a combination of concept-based and interpreter-based approaches. The book has an implementation-oriented focus and features conceptual and programming exercises that give students practical experience applying language theory and concepts. The book also showcases the construction of a progressive series of language interpreters in Python that cover the implementation of a host of core language concepts such as scope, first-class functions, and parameter passing. Other programming styles, including logic/declarative programming, and compelling language features, such as first-class continuations, are also discussed. Concepts are presented in Python, Scheme, JavaScript, Ruby, ML, Haskell, Prolog, and various other programming languages. This book is intended as a general-purpose textbook for a course on programming languages.