-able and -ible

The suffixes “-able” and “-ible” are both used to form adjectives meaning “possible, capable of, suitable for, or causing.” Of the two, “-able” is much more common: it is what's known as a “living” or “productive” suffix, meaning that it is still being used to create new words. 

What is the rule for able and ible?

Here is the rule: If you remove -able from a word, you are left with a complete word (renewable, renew). If you remove -ible from a word, you are not left with a complete word (sensible, sens). But note that accessible, contemptible, digestible, flexible and suggestible are among the exceptions to this rule.

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