Metric spaces: 100 years

I only knew Fréchet as a mathematician, who came up with the notion of derivative in normed vector spaces, which made sense to me. It turnes out that he is behind a number of fundamental definitions we are using today.

Maurice Fréchet introduced metric spaces in his work Sur quelques points du calcul fonctionnel, Rendic. Circ. Mat. Palermo 22(1906) 1-74.

The term compact was introduced by Fréchet in 1906.

Biography: Maurice René Fréchet