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I'm not a native English speaker and I was wondering what is the rule that decides whether to write double letter before -able.

In programming, we have abused the (English) language in new ways, needing to name attributes of objects, which are derived from verbs, e.g.:

freezable
pushable
poppable
stoppable
interruptible
mappable

And so on. What is the rule? Does p always repeat while the other letters do not? :)

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    I'd answered if you didn't asked for the rules, because I think I have a solution for you. Most, if not all, of a noun-able are listed in dictionaries. For those verb-able, it's simple: double it in -able like when you double it in -ing, and a good dictionary would show how you would spell the -ing form explicitly. For example, freeze -> freezing (click on "Word Forms"), so freezable; push -> pushing, so pushable; pop -> popping, so poppable, and so on. This doesn't cover interruptible, though. Commented Sep 23, 2014 at 17:55
  • Also, when in doubt, you can always consult dictionaries or other online resources. Google is really useful. Commented Sep 23, 2014 at 17:57
  • Does this answer your question? Why is there one P in "hoping" and two P's in "hopping"?
    – user3395
    Commented May 24, 2020 at 21:19

2 Answers 2

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If it's a short vowel sound and a single consonant, then you double the consonant to signify that the vowel sound is supposed to stay short:

map > mappable
hit > hittable
cancel > cancellable

Otherwise (if the vowel is already long, or if there is more than one consonant already) you don't need to double anything, because the vowel sound won't change anyway:

junk > junkable
excite > excitable
quote > quotable

If you don't double the consonant when you're supposed to, it will look like the vowel is supposed to be long:

mapable = "may-puh-bull", not "map-uh-bull"

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    That's harsh, as us non-natives also fight with the pronunciation :). Didn't know that junk was a verb.
    – the swine
    Commented Sep 23, 2014 at 17:03
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    Exception: when the verb ends in "c", it becomes "ck": mimic -> mimickable
    – Ypnypn
    Commented Sep 23, 2014 at 19:11
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    I think "cappable" versus "capable" might be a good example. Cappable isn't a very common word unless you are a brewer looking for cappable bottles, but I think it illustrates the difference in doubling the consonants because of vowel sounds.
    – ColleenV
    Commented Sep 23, 2014 at 19:44
  • hittable [buzzer]
    – Lambie
    Commented May 24, 2020 at 21:57
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    @Hellion There are other issues, too. For example, your guidance apparently requires "edittable", which is incorrect. Commented Mar 2, 2022 at 19:35
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  • freezable
  • pushable
  • poppable
  • stoppable
  • interruptible
  • mappable

Quite simply,

  1. If the base word is in CVC form, double the final consonant before -able.

Examples:

  • Pop (CVC form) -> poppable
  • Stop (CVC form) -> stoppable
  • Map (CVC form) -> mappable

  1. Do not double the final consonant before -able if:

    • the final consonant in base word is preceded by a digraph
    • the final consonant in base word is preceded by a diphthong
    • the final consonant in base word is followed by magic/silent e
    • the construction is CVCC or CVVC.

Examples:

  • Freeze + able -> freezable (don't double the z because it's followed by magic e)
  • Push + able -> pushable (don't double sh because it's a digraph)
  • Interrupt + ible -> interruptible (don't double the t because the construction is CVCC)

Related answers:

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