As the title says, what is the correct plural form of regex?

To my knowledge, regex is an abbreviation for regular expression. I see that some sources suggest regexes and regexen are both correct. The latter plural form sounds maybe German?

Any suggestions?

  • Hello, Alireza. This is general reference. Wikipedia has << The phrase regular expressions, and consequently, regexes, is often used to mean the specific, standard textual syntax (distinct from the mathematical notation described below) for representing patterns for matching text. >> Wikipedia is a better recognised source than the one you link to. // Appearance in the OED of 'regex' and 'regexes' would certainly confirm wordness, but I think you can use them safely in all but the most formal registers. Aug 19, 2019 at 14:07
  • VTC. Sorry, I voted to leave open by mistake.
    – Xanne
    Aug 19, 2019 at 23:24
  • why the downvote?
    – user1984
    Aug 20, 2019 at 4:41
  • 2
    I prefer "regices" like "index -> indices" or "vortex -> vortices".
    – rory.ap
    Jun 5, 2020 at 14:46
  • 4
    If you've used more than one of them, you'll know that the plural of "regex" is "regrets."
    – cjs
    Mar 14, 2022 at 23:46

1 Answer 1


This is domain-specific jargon (the domain being Information Technology), rather than standard English, and thus may not conform to the rules. Wiktionary and Quora both give regexes or regexps; while I don't find regexen unlikely, I've not actually seen/heard it used, and it would not come to mind immediately for me.

(You are correct that it is an abbreviation/shorthand for regular expression)

  • 1
    I've never seen it either, but I wouldn't put it past programmers to use it; as well as a third-declension Latin plural regeges. Aug 19, 2019 at 20:25
  • 1
    Actually, the plural of "regex" is "regrets" (twitter.com/ifosteve/status/1190348262500421634)
    – Kankaristo
    Mar 28, 2022 at 14:46
  • @Kankaristo - Been there, done that, tossed the T-shirt on a bonfire. See similar comment on the question itself (from cjs). Mar 28, 2022 at 15:17
  • I happened to see "regexen" on a StackOverflow answer (stackoverflow.com/questions/1828236/…). I wondered why they were conjugating it like that, so found this post.
    – Q Z
    Sep 5, 2022 at 15:33
  • 1
    @QZ my guess is a copy of "ox(en)". (I found this post searching if anyone thought about regices)
    – minirop
    Oct 17, 2023 at 20:08

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