Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I know very little in the way of math history, but I question that was bothering me recently is where the terms open and closed came from in topology. I know that it's easy to ascribe a sense of openness/closedness to said sets, but I feel like there are a lot of other, more appropriate words that could have been used. On a related note, I was wondering who first developed the idea of open/closed sets, and who first used those words to describe them.

share|cite|improve this question
related threads: 1 2. – Alexander Gruber Jun 13 '14 at 23:11

This answer addresses your question on who first actually used the words "open" and "closed" to describe open and closed sets. It seems, according to this article, like the first mention of this language was in René Baire's doctoral dissertation,

Sur les fonctions de variables réelles Annali di matematica pura ed applicata (3), 3 (1899), pp. 1–123

which I believe first appears in page 7 of the document in the context of defining an "open domain." The term itself was first actually defined by Lebesgue in his dissertation, Intégrale, longueur, aire, (which I cannot find an online copy of) for the purpose of setting up Lebesgue measure.

I think the rest of your question should be addressed to your satisfaction between the linked article and related MSE/MO threads.

share|cite|improve this answer

the followings archives corresponds to the doctoral thesis of Henri Lebesgue:

You can search for Analysis situs, old name for the actual topology.Lebesgue and Rham (french mathematicians) wrote about that subject.


Hugo Mancera Colombia

share|cite|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.