Spelling correctly is possible street sign
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Well! We’ve reached the end! Almost. So far, we’ve explored three aspects of the -able/-ible spelling conundrum. We’ve learned that -able is, by far, the more common of the two suffixes – and therefore, a better choice if you’re guessing a spelling. We’ve learned that if you can think of a similar suffix to add to the end of a word, the first letter of that similar suffix should point the way to the correct choice of -able vs. -ible. And we’ve learned definitively when to use -able. Now let’s explore when to use -ible, and finish answering this question once and for all!

Words that end in –ible: when the stem is not a word

Remember how you can often take a word in English and simply add –able to the end? Well, a somewhat opposite situation exists with –ible. If you were to take a word with –ible and remove that suffix, you’d be left with…well, not exactly a word in English. For example, the word possible without the suffix reveals the stem poss, which isn’t a word. You could say the same for the word irascible: there really isn’t a word irasc in the English language!

So, in a nutshell: words ending in –ible often do not exist as words when the suffix is removed. Here are other examples:

  • miscible
  • vincible
  • rescissible
  • audible
  • indelible
  • fungible

Words that end in –ible: when the stem is not a word: the exceptions

These exceptions are brought to you by the letters c and g. Specifically, these exceptions occur when the stem-that-is-not-a-word ends in the letter c sounding like a hard /k/. They also occur when the stem-that-is-not-a-word ends in the letter g sounding like a hard /g/. To preserve these hard sounds, we use the suffix –able. Here are some examples:

  • amicable
  • judicable
  • refragable
  • indefatigable

Similar suffixes and –ible: a recap

The trouble with the rule above is that it doesn’t always work. Remember the rule from our second post about similar suffixes? The suffixes –ion or –ive begin with the letter “i.” If you can put these suffixes at the end of a stem and come up with a word, the spelling –ible will be the correct one. Here are a few other examples to help cement this rule in your mind:

  • flex / flexion / flexible
  • combust / combustion / combustible
  • perceive / perceptive / perceptible
  • persuade / persuasive / persuasible
  • submerge / submersion / submersible

One last rule…regarding –able after the sound \ī\

Sorry to put this at the end, but this is a good rule all the same. If you have a word stem that ends in the sound \ī\, use the suffix –able to end the word. This is a very…*ahem*…reliable rule! Examples include:

  • reliable
  • friable
  • viable
  • classifiable
  • dryable
  • buyable
  • flyable

Note that on the last three words, there is another common spelling rule that is flouted. Usually, when you add a suffix to a word that ends in y, you change the y to an i, and then add the suffix. Not in these three words!

WHEW! We’re finally finished answering the question of when to spell that suffix –able, and when to go with –ible. For such a simple question, it is dizzyingly difficult to answer. But as we’ve shown, it is…*ahem*…conquerable. Well done!

Image by Gerd Altmann from Pixabay