This English translation of Vom Wesen der Sprache, volume 85 of Martin Heidegger's Gesamtausgabe, contains fascinating discussions of language that are important both for those interested in Heidegger's thought and for those who wish to think through the nature of language. The guiding theme of these reflections on language is found in Heidegger's lecture notes for a 1939 seminar that focused on J. G. Herder's treatise On the Origin of Language. This course, given just after the completion of his Contributions to Philosophy, sheds new light on the force of language in Heidegger's thought and shows the first openings to his later, better-known works dedicated to the topic of language. The result of this project is to outline how it is that thinking the being of the word moves out of metaphysics into the poetic word and its relation to history. A crucial work, this course brings the reader close to a decisive moment in Heidegger's thought, letting us see how he struggled forward to new ways of thinking how it is that "language as language" can be thought.