Karl Theodor Wilhelm Weierstrass (October 31, 1815 - February 19, 1897) was a German mathematician who is often cited as the father of modern analysis. His interest in mathematics began while he was a child, but was sent to the University of Bonn upon graduation to prepare for a government position. He ignored his planned course of study, and continued private study in mathematics. He left the university without a degree. After that he studied mathematics at the University of Munster and his father was able to obtain a place for him in a teacher training school.During this period of study, he attended the lectures of Christoph Gudermann and became interested in elliptic functions. Besides mathematics he also taught physics, botanics and gymnastics. He was interested in the soundness of calculus. At the time, there were somewhat ambiguous definitions regarding the foundations of calculus, and hence important theorems could not be proven. He is best remembered in mathematics for the formal definition of continuity of a function. Using this definition and the concept of uniform convergence, he was able to write proofs of several then unproven theorems such as the intermediate value theorem, the Bolzano-Weierstrass theorem, and Heine-Borel theorem. He also made significant advancements in the field of calculus of variations. He was immobile for the last three years of his life, and died from pneumonia in 1897 at the age of 81.