Knowledge of languages ​ ​ not only strengthens memory, but also develops thinking, saves from depression and even postpones Alzheimer's disease. Want to teach, but not sure what will happen? Then keep in mind: a foreign language is the only thing worth knowing at least badly. The book tells about the features of languages, provides a variety of ways to learn them, provides links to additional materials: books and resources (free), and also describes the author's experience in learning languages.