The Meaning of Relativity All New Modern Translation 2025 This book was based on the four lectures given at the Princeton University, in 1921, and it was originally published in German. The book was later translated into English and published with the title "The Meaning of Relativity". After over 100 years, for anyone who wants to really understand relativity, with some mathematical background, this book still remains the best introduction to relativity, for both special relativity and general relativity.