I need to name an interface in a program I'm writing as being able to collide, but I've seen use of both collideable and collidable in projects with a similar type. Both of them look right in some ways, and wrong in others. Which spelling is more correct?

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    According to google: "collidable" About 46,300 results; "collideable" Did you mean: collidable? About 6,230 results. But this may just reflect the American English prevalence among programmers... :) Commented Feb 7, 2011 at 10:18
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    That's what I had figured, too. I'm glad I'm Canadian, I can pick and choose my spellings. >:D Commented Feb 7, 2011 at 16:52

2 Answers 2


Short answer: There's no clear choice; take your pick.

Long answer: Neither collideable nor collidable is a word you're likely to find in a dictionary, but in your context using it (one of them) may be exactly the right choice. As for the spelling preference, Wikipedia's detailed article on American and British English spelling differences says:

Before -able, British English prefers likeable, liveable, rateable, saleable, sizeable, unshakeable, where American practice prefers to drop the -e; [borderline: tradeable, smokeable, driveable, shareable] but both British and American English prefer breathable, curable, datable, lovable, movable, notable, provable, quotable, scalable, solvable, usable, and those where the root is polysyllabic, like believable or decidable. Both forms of the language retain the silent e when it is necessary to preserve a soft c, ch, or g, such as in traceable, cacheable, changeable; both usually retain the "e" after -dge, as in knowledgeable, unbridgeable, and unabridgeable. ("These rights are unabridgeable.")

The "polysyllabic" rule would point towards collidable, but elsewhere, a search brings up the following poly-syllabic words ending in eable (other than soft c, ch, g instances, of which there are many) (I haven't checked their provenance):

canoeable diagnoseable disagreeable dislikeable fireable foreseeable handleable hireable machineable microwaveable removeable settleable throttleable unforeseeable unnameable upgradeable whistleable

Or you may want to look specifically at -able words formed from verbs ending in -de, and decide whether -dable or -deable is preferable:

abradable codable decidable degradable dividable evadable excludable extrudable fadable gradable guidable hidable includable persuadable ridable/rideable slidable tradable/tradeable upgradable/upgradeable wadable/wadeable

It seems that analogy with dividable and decidable (the closest?) would suggest collidable. (But if you still prefer collideable, it's fine to use it…)

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    Nice answer. Of your second list, I would also remove the "-ee" words (such as "forseeable"), because removing an "e" there would also change the pronunciation. I'd also be tempted to remove the words that are compounds based on single-syllable "-eable" compounds (eg "dislikeable"), and also "fireable" since "fire" is a single syllable in most dialects. That tips the balance slightly further towards "collidable" :)
    – psmears
    Commented Feb 12, 2011 at 13:51

-able forms adjectives that mean:

  • able to be: calculable
  • due to be: payable
  • subject to: taxable
  • relevant to, or in accordance to: fashionable
  • having the quality to: suitable, comfortable

Collidable would mean able to be collided, not able to collide. Instead of collidable, you can use hittable, which would mean able to be hit.

As per choosing between collidable and collideable, the adjective that derives from cite is citable; in the same way, you should write collidable, not collideable.

  • "Able to be collided" is good enough for me; the interface is for objects that are handled by acollision detection system, and its siblings are interfaces named IDrawable and IUpdateable. (Yeah, with an E.) Commented Feb 7, 2011 at 8:00
  • Collidable, collideable, and hittable are not listed in the dictionary I have (the NOAD). The Corpus of Contemporary English contains sentences using hittable; the word is found with a frequency of 0.10 per million.
    – apaderno
    Commented Feb 7, 2011 at 8:01
  • Collidable, and collideable are not found in the Corpus of Contemporary American English, nor in the British National Corpus.
    – apaderno
    Commented Feb 7, 2011 at 8:28

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