After graduating in 1892, he placed first in the agrégation, a competitive civil service examination leading to the position of professeur agrégé.

That year, Borel started a four-year stint as a lecturer at the University of Lille, during which time he published 22 research papers.

[4] In 1901, Borel married 17-year-old Marguerite, the daughter of colleague Paul Émile Appel; she later wrote more than 30 novels under the pseudonym Camille Marbo.

One of his books on probability introduced the amusing thought experiment that entered popular culture under the name infinite monkey theorem or the like.

[5] John von Neumann objected to this assignment of priority in a letter to Econometrica published in 1953 where he asserted that Borel could not have defined games of strategy because he rejected the minimax theorem.

Besides the Centre Émile Borel at the Institut Henri Poincaré in Paris and a crater on the Moon, the following mathematical notions are named after him: Borel also described a poker model that he coins La Relance in his 1938 book Applications de la théorie des probabilités aux Jeux de Hasard.