Words Ending In –able and –ible

We previously did a post on words ending in ‘–ance’ and ‘–ence’. Another such pair of words is ‘–able’ and ‘–ible’.  Words ending in these suffixes are adjectives that refer to the ‘ability to’ or ‘necessity to’. For example ‘acceptable’ or ‘possible’. The problem is in the difficulty to remember which ending to use, ‘-able’ or ‘-ible’. What makes it even more confusing is that the two are pronounced identically.  So, when do use ‘-able’ and when do use ‘-ible’?

English being English, there is no rule; but generally, these hints work most of the time:

* Add ‘–able’ when the root word is a complete word. For example:

Accept + able = acceptable

Suit + able = suitable

Depend + able = dependable

* Add ‘–able’ when the root word ends in ‘e’, but first drop the ‘e’. For example:

Excuse – e + able = excusable

Value – e + able = valuable

Desire – e + able = desirable

* Add ‘–ible’ when the root is not a complete word. For example:

Horr + ible = horrible

Permiss + ible = permissible

Aud + ible = audible

* Add ‘–able’ when the word is new or modern. For example:

Email + able = emailable

Surf + able = surfable

Network + able = networkable

* As always is the case with the English language, there are exceptions. That is, none of the above apply. For example:

‘Contempt’ is a complete word, but ‘–ible’ is added, not ‘–able’ … contemptible

‘Response’ ends in ‘e’, but ‘–ible’ is added after dropping the ‘e’, not ‘–able’ … responsible

So, what should you do when you’re confused as to which suffix to use? Do one of the following:

1. Learn the spellings.

2. Look the word up in the dictionary.

3. Remember the hints above.

4. If there’s no dictionary around and you can’t remember either the spellings or the hints, just add ‘–able’. There is 5:1 chance you’ll get it right, because according to a research, there are only about 150 words that end in ‘–ible’. All the rest end in ‘–able’.

What do you do to remember which suffix to use?

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2 Responses

  1. Hi – this is a great post -it’s the clearest explanation I’ve found of when to use these two endings. Your readers might be interested in my blog which is a relaxed and friendly guide to grammar, punctuation and writing well. It doesn’t cover this ‘ible’/’able’ topic though – and I’m not going to bother now – I’ll just send people here! Thanks.



  2. Thank you, Deborah, for your encouraging words. I truly appreciate them.


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