Some mathematical concepts are ended with "-oid", such as Matroid, greedoid, groupoid. What does that mean? Do these concepts share something in common? Thanks!
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i know humanoid means a robot – S L Jan 11 '13 at 00:10
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It's not specifically math terminology. See here. – David Mitra Jan 11 '13 at 00:11
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@DavidMitra: Groupoid is like group, and matroid is like ..., and Greedoid is like ...? – Tim Jan 11 '13 at 00:13
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2Matrix and, um, Greedo from Star Wars? – David Mitra Jan 11 '13 at 00:13
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2Hopefully the string hemorrh never makes into the mathematical lexicon. – copper.hat Jan 11 '13 at 00:22
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It’s something like “something like”. – Lubin Dec 26 '13 at 19:33
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Means "bed", "incomplet","deficient" or "weak". For exemple: Grupoid is a algebric struture "deficient" that is quase a Group.
Elias Costa
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2@Elias, a groupoid is a category in which all arrows are iso. This includes the category $\bf Group$ , which is a monoid (ie, one-object) groupoid. See: http://ncatlab.org/nlab/show/groupoid – alancalvitti Jan 11 '13 at 00:25
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@Elias, - just wanted to clarify, groupoids are generalizations of groups, but in what way are they deficient or quasi? (There's an interesting if cryptic remark in Lawvere & Rosebrugh's Set Theory for Mathematics to the effect that most of what we know about groups carries over to groupoids.) – alancalvitti Jan 11 '13 at 00:39
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3Sounds a lot like "-ish." Such a shame we didn't end up with matrish or groupish. – Jesse Madnick Jan 11 '13 at 00:40
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If you have a "center" of an object, it means "equidistant" from the edges (spacially).
If you have a centroid, it means the weighted "center" of an object, where the weightS are something like the density of the material.
Here the "oid" is a reference to the "weighted" (e.g. center) property, not the literal one.
Tom Au
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