The English philologist and author J. R. R. Tolkien created several constructed languages, mostly related to his fictional world of Middle-earth. Inventing languages, something that he called glossopoeia (paralleling his idea of mythopoeia or myth-making), was a lifelong occupation for Tolkien, starting in his teens.
Tolkien's glossopoeia has two temporal dimensions: the internal (fictional) timeline of events in Middle-earth described in The Silmarillion and other writings, and the external timeline of Tolkien's own life during which he often revised and refined his languages and their fictional history. Tolkien scholars have published a substantial volume of Tolkien's linguistic material in the History of Middle-earth books, and the Vinyar Tengwar and Parma Eldalamberon journals. Scholars such as Carl F. Hostetter, David Salo and Elizabeth Solopova have published grammars and studies of the languages.