List of mathematical portmanteaus

Asked Jul 20 '21 at 18:46

Active Jul 20 '21 at 19:22

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Students (including myself) are always fascinated when they learn words like "clopen" set for closed and open in topology, or "club" set for closed and unbounded in set theory. I also learned recently that injective/surjective were a sort of portmanteau in French.

What other portmanteaus/ fun contractions are there in math? I'm having a hard time thinking of more than a couple.

edited Jul 20 '21 at 19:22

J.-E. Pin

40,163

asked Jul 20 '21 at 18:46

Maxim Gilula

1,485

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"Cadlag" is an acronym from a French phrase, and is sometimes used when writing in English. – Michael Hardy Jul 20 '21 at 18:51
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"iff" stands for if and only if. – Kurt G. Jul 20 '21 at 19:03
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Somewhat the opposite of joining words together is cleaving one in two: eg, Dirac's "bra-ket" notation from "bracket". – Blue Jul 20 '21 at 19:12
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"Quabla" is the quadratic nabla operator. – Kurt G. Jul 20 '21 at 19:18
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@KurtG.: In this answer, I mention John Conway's compulsion to follow "iff" with "thenn" ("then and only then"). Comments point out other Conwayisms: "whenn", "onne" (which was my own suggested answer to that question), "threee". The MathWorld "Exactly One" entry mentions "onee" (note the alternate spelling, which I would take to be the correct one), "twoo", and "threee". – Blue Jul 20 '21 at 19:22
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poset for partially ordered sets – ashK Jul 20 '21 at 19:28
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LOST: Language Of Set Theory, and an accurate description of the feelings of many beginners of this subject.... In Set Theory, "Club", "Diamond" and "Diamond$^+$" are axioms, consistent with but independent of ZFC that are usually denoted by playing-card symbols . The axiom "Club" is a different thing from a club set. K.Kunen uses c.u.b. for closed-unbounded. And a result by Arnold Jensen about c.u.b. sets has been called "shooting a cub". – DanielWainfleet Jul 20 '21 at 21:21
A nowhere-dense perfect subset of $[0,1]$ with positive Lebesgue measure is called a fat Cantor set. – DanielWainfleet Jul 20 '21 at 21:46
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"irrep" is an irreducible representation (of a group) – Kurt G. Jul 22 '21 at 12:26
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A rep-tile is a shape that tiles itself. – Blue Jul 25 '21 at 11:58
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Herewith, I solemnly make the proposal to call irrep-tile a shape that does not tile itself. – Kurt G. Jul 25 '21 at 17:18
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A Gibonacci sequence is a generalized Fibonacci sequence. – Kurt G. Sep 09 '21 at 11:21

List of mathematical portmanteaus

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