Words that end with -able and -ible are difficult to spell because they’re pronounced the same way. Here are some general guidelines to help you decide which ending to use. But be careful: there are exceptions!
- If the corresponding noun ends in -ation (notation), add the suffix -able: notable
- If the corresponding noun ends in -sion or -tion (division), add the suffix -ible: divisible
- In most other cases, when the root word is a complete word (understand), add the suffix -able: understandable