What is the correct plural form of the portmanteau mutex. Is it mutexes or mutices?
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14I think it should be "mutexen" but I'm crazy. Don't mind me. – Chris Lutz May 15 '09 at 03:37
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2This really should at least be a wiki. – gnovice May 15 '09 at 03:49
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8Mutexen! I saw a flock of mutexen! There were many of 'em. Many much mutexen. Out in the apps- in the appes- in the appsen. – bsneeze May 15 '09 at 04:29
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1@ChrisLutz: Was that really you or did RMS hack your account? – R.. GitHub STOP HELPING ICE Dec 11 '12 at 03:47
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2Unfortunately the original question lacked any tags to give a context, but if the context is POSIX threads, the authoritative answer can be seen in the text of POSIX: http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_09_03 – R.. GitHub STOP HELPING ICE Dec 11 '12 at 03:53
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4when I have more than one mutex the answer is usually deadlock. – CashCow Jan 20 '14 at 12:23
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I strongly believe that it should be 'muteci'. But it is just me. – wintermute Jul 27 '18 at 18:38
9 Answers
From a purely linguistics point of view, the correct usage is mutexes because the word mutex is not Latin in origin. Prescriptivists would wail in anguish if mutices were to enter regular usage.
The -ices usage (e.g., the plurals of index and vertex) is falling out of favor. Indexes and vertexes are both correct usage, for example.

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42"Indexes and vertexes are both correct usage" -- Bah. Humbug! Call me old fashioned, but I still use the -ices forms. – dmckee --- ex-moderator kitten May 15 '09 at 13:31
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1Falling out of favour because today's youth have little to no knowledge of one of the primary languages influencing English and most other European tongues. Hm. Not a good excuse not to use the correct form. Having said that, mutices is incorrect because its base isn't in Latin. – Engineer Dec 02 '18 at 10:42
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*Indices* may be falling out of favor, but I haven't seen any indication that *vertices* is. In fact, in my graph theory course a few years ago, it was common for students to slip up and say, "verticee" when they meant, "vertex"! – Dominick Pastore Sep 23 '20 at 21:30
Everyone knows that the correct answer is Mutii.

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Hah! For some reason that was actually the first thing to spring to mind for me. – gnovice May 15 '09 at 03:45
Mutexes. It's correct in a de facto manner--- the vast majority of people (in my experience, certainly) call them mutexes, not mutices, and English is a language that's defined by use. :)

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As mutex is short for "mutual exclusion", I would only imagine that "mutual exclusions" would become mutexes. Mutices would be confusing. Better to be unambiguous.
As a side note: it's not a portmanteau, or it would be a mutsion.

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2"Mutex" is a portmanteau of "MUTual EXclusion." http://en.wikipedia.org/wiki/Portmanteau – jason May 15 '09 at 03:30
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1I was under the impression that portmanteaus were required to be the beginning of one word concatenated with the ending of another. The article doesn't have any examples of portmanteaus that do not follow this pattern (except for Jabberwocky words), but does not say that this condition is required. So you may be correct. – rlbond May 15 '09 at 03:38
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INTERnational NETwork -> Internet. PICture ELement -> Pixel. WIreless FIdelity -> Wifi. HAZaradous MATerial -> Hazmat. – jason May 15 '09 at 03:45
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4@Jason: nice list of words, but are they portmanteaux? :P I'd call yours neologisms or syllabic abbreviations. don't forget bit -> binary digit. – Lucas May 15 '09 at 04:28
There's no official correct form because 'mutex' hasn't gained wide enough circulation to enter any of the major English dictionaries. Thus, the most correct term is whatever is used most by people. And I think that Google hits are a pretty good indicator of (relative) usage frequency, as great_lama has pointed out.
Other English nouns that end in -ex or -ix:
- Affix
- Annex
- Apex
- Appendix
- Cervix
- Circumflex
- Complex
- Cortex
- Crucifix
- Duplex
- Helix
- Ibex
- Index
- Infix
- Latex
- Matrix
- Phoenix
- Prefix
- Postfix
- Reflex
- Remix
- Suffix
- Vertex
- Vortex
And lots more less common words. If you look up these in the dictionary, you'll find that most of them have both plurals shown as acceptable. Several have only the -exes/-ixes form, but few or none (depending on the dictionary you use) have only the -ices form.
In conclusion, I believe mutexes to be the correct plural form of mutex.

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Either/or. I've seen both (though mutexes is considerably more common).
Mutex is not in any real dictionary I know of, so there's no "official answer."
Index can be pluralized to indexes or indices, though, so it makes sense that mutex could follow suit.

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I think that the hysterical raisins (in this case the fact that "mutex" is a portmanteau) should not be given too much weight in resolving such issues. Perhaps it would be more useful to consider similar words and their usage; reflex -> reflexes for example.
Or, use the simplest choice: most pluralizations in english use -s/-es (depending on whether last letter is a perceived vowel); in this case -es.
I guess I can't see any reason to use the alternative, except as some sort of tribute to Latin, once thought to be the noblest of all languages. :)

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