A letter or group of letters added at the end of a word to make it a new word is termed a suffix. There are numerous examples of suffixes, and they include '-ity' as in possibility; and '-ion' as in action.
Adding suffixes are likely to be wrongly spelt. Meanwhile, in this article we are focusing on words ending in '-able' and '-ible'. They all form adjectives and the list and videos below show some examples, their root words, spelling when suffix is added and synonym to show their meaning.
The next list is a video on words ending in '-IBLE'.