Leonhard Euler
Swiss mathematician (1707–1783)
Leonhard Euler ( OY-lər; 15 April 1707 – 18 September 1783) was a Swiss polymath who was active as a mathematician, physicist, astronomer, logician, geographer, music theorist and engineer. He founded the studies of graph theory and topology and made influential discoveries in many other branches of mathematics, such as analytic number theory, complex analysis, and infinitesimal calculus. He also introduced much of modern mathematical terminology and notation, including the notion of a mathematical function. He is known for his work in mechanics, fluid dynamics, optics, astronomy, and music theory. Euler has been called a "universal genius" who "was fully equipped with almost unlimited powers of imagination, intellectual gifts and extraordinary memory". He spent most of his adult life in Saint Petersburg, Russia, and in Berlin, then the capital of Prussia.
Euler is credited for popularizing the Greek letter
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![Photograph of Charles Darwin; the frontispiece of Francis Darwin's The Life and Letters of Charles Darwin (1887) has the caption "From a Photograph (1854?) by Messrs. Maull. And Fox. Engraved for Harper's Magazine, October 1884."[1] In an 1899 paper, Francis Darwin wrote that "The date of the photograph is probably 1854; it is, however, impossible to be certain on this point, the books of Messrs. Maull and Fox having been destroyed by fire. The reproduction is by Mr. Dew-Smith, who has been at s](/_next/image?url=%2Fassets%2Fwiki%2Fcharles-darwin.webp&w=3840&q=85)