Two common suffixes in English are ‘-able’ and ‘-ible’. It is sometimes difficult to know which one to use. -able descends from the Latin ‘abilis’ and has resulted in the formation of words such as capable, amiable and favorable, as well as many other English formations.
The suffix is also in wide use because of its association with the word able, and has resulted in many word formations similar to drinkable (able to be drunk).
Often added to words of English or French origin, -able is used much more widely than -ible. However, there are still about a hundred common words that take -ible, including: accessible, admissible, audible, convertible, credible, digestible, discernible, edible, eligible, fallible, feasible, forcible, gullible, horrible, intelligible, legible, negligible, perceptible, permissible, plausible, possible, responsible, susceptible, tangible, terrible and visible.