Leonhard Paul Euler (15 April 1707 – 18 September 1783) was a pioneering Swiss mathematician and physicist who spent most of his life in Russia and Germany. His surname is pronounced /ˈɔɪlər/ OY-lər in English[3][4][5][6] (German pronunciation: [ˈɔʏlɐ]); the common English pronunciation /ˈjuːlər/ EW-lər is generally considered incorrect.[7]