Italian mathematician best know for contributing to the development of relativity. He and Gregorio Ricci-Curbastro developed absolute differential calculus (1900). This was employed by Albert Einstein in formulating the general theory of relativity (1915). Levi-Civita's most significant contribution to mathematics was to extend the notion of parallel lines to curved spaces (1917). This and other work influenced the evolution of absolute differential calculus into tensor calculus, which enables unified treatments of electromagnetic and gravitational fields.