Dear Michael, Thank you very much for sharing this piece of history. I, personally, am always deeply interested to learn of the stories behind the mathematics, and the people responsible for it, that have been fundamental in shaping what we understand to be category theory today. In the interest of posterity, I have a slight amendment to the etymology you described. I should preface what follows by making it clear that my understanding is based only on the literature, rather than personal experience, and so may not accurately reflect the actual history (in which case I would be glad to be corrected). (On fundamental/standard constructions) The terminology employed by Godement (on p. 271 of the 1958 "Topologie algébrique et théorie des faisceaux") was "la construction fondamentale", i.e. "the fundamental construction". It was thus Godement rather than Maranda who introduced this terminology; Maranda appears to be the only one who continued to use that terminology in later work. Huber then employed the terminology "standard construction" for the notion of comonad (in §2 of the 1961 "Homotopy Theory in General Categories") – monads are instead called "dual standard constructions". It does not appear to be until around 1968 that the terminology "standard construction" appears in reference to the concept of monad rather than comonad. (The seemingly misinformed assertion that Godement introduced the terminology "standard construction" appears, perhaps for the first time, in the 1969 Proceedings of "Seminar on Triples and Categorical Homology Theory", which may be where confusion has arisen.) (On triples) I believe the paper of Eilenberg and Moore in which the terminology "triple" first appears is the 1965 "Adjoint functors and triples" (I did not find the terminology "triple" in "Foundations of Relative Homological Algebra"). (Incidentally, in Dubuc's 1968 paper "Adjoint triangles", he refers to the terminology "triplex", but this appears to be a typo, as I cannot find that terminology elsewhere.) (On monads) In a 2009 email to the categories mailing list (https://www.mta.ca/~cat-dist/archive/2009/09-4), you recounted the same story about the origin of the terminology "monad", except that you recalled the one who proposed the terminology was Jean Bénabou. This seems likely, since, as far as I can tell, the term first appears in Bénabou's 1967 "Introduction to bicategories" (p. 39), where the terminology is justified in a footnote on p. 40. Best, Nathanael On 8 Nov 2023, 22:22 +0100, Michael Barr, Prof. , wrote: People seemed to enjoy my history of the founding of TAC, so I thought you might enjoy my sharing of other historical notes. This construction was introduced in Godement's book Théorie des faisceaux in connection with his resolution of sheaves by "faisceaux mous" (soft sheaves) which are an injective class. He called this "la construction standarde". It is not clear whether this was intended to name them or merely describe them. At any rate, around 1960, Benno Eckmann and his students took as a name and called them standard constructions. One of the students, Peter Huber, told me that they were having trouble, in particular cases, verifying the associative law. And then he noticed that in all the cases he knew, the functor T had the form UF, where F --| U. He wondered if every adjoint pair gave rise to a standard construction and proved that it did. Then another student, Heinrich Kleisli, showed that the converse was also true. That gave us the well-known Kleisli construction. In 1963 Samuel Eilenberg and John Moore published a monograph called Foundations of Relative Homological Algebra in which they used this construction as basic. Only they didn't call them standard constructions; they called them triples. I once asked Sammy why and he replied that it didn't seem like an important concept and it didn't seem worth it to spend a lot of time worrying about the name. This is in stark contrast with the time he and Henri Cartan spent thinking about the name for their basic sequences. There is a story, perhaps apocryphal, that their book was in proof stage before they settled on the exact name. So triple was name Jon Beck and I were using in our joint work on homological algebra. Then in 1966 there was a category meeting in Oberwohlfach and there was a lot of discussion of a better name. The next bit of the story comes out of my extremely fallible memory and could well be mistaken. One day at lunch I was sitting next to Anders Koch and he asked what I thought about the name monad. I thought (and still think!) it was a pretty good name and so he proposed it and the assembled crowd agreed and adopted it. I would have too, but Jon rejected it. Why, I asked him. He did not think it a good name and refused to use it. He said there was no point in replacing one bad name by another. Since we were collaborating and since he was even more stubborn than me, that's they way it was. In our papers, Jon insisted on putting functions to the right of their arguments, just like reverse Polish. Then we stopped collaborating and, by 1980, I think I was about ready to start using monad. But then TTT came along and the alliteration was just too good to pass up. Charles Wells agreed on those grounds. And what about fundamental construction? I spent six and a half months at the ETH in Zurich. A few days after I arrived, I got a phone call from Peter Huber, the aforementioned former student of Eckmann's. He had just received from Math Reviews a paper written by Jean-Marie Maranda that used that term for the concept and Huber asked me if there was any way to stop that proliferation of names. As far as I know, that was the only place that term was ever used. Michael You're receiving this message because you're a member of the Categories mailing list group from Macquarie University. To take part in this conversation, reply all to this message. View group files | Leave group | Learn more about Microsoft 365 Groups