What is the rule of adding ible and able?

There isn't a single, simple rule for adding "-ible" or "-able" to words. It's more about understanding how the suffixes work and how they are used to create new words. Here's a breakdown:

-able:

* Generally indicates "capable of being" or "suitable for."

* Examples: Breakable (capable of being broken), washable (suitable for washing)

* Often added to verbs:

* Examples: Change + able = changeable, manage + able = manageable

-ible:

* Often used for words derived from Latin or French:

* Examples: Visible (from the Latin "visibile"), audible (from the Latin "audibilis")

* Sometimes indicates "capable of being" but often has a more specific meaning:

* Examples: Incredible (not believable), edible (fit for eating)

Tips for Choosing:

* Think about the meaning: Consider what the word means and if the meaning fits the concept of being capable of something, being suitable for something, or having a specific characteristic.

* Check a dictionary: When in doubt, check a dictionary to see if the word exists and how it's spelled.

* Practice: The best way to learn is to practice using these suffixes in different contexts.

Important Note: While there are some patterns, there are many exceptions to the rules. There are also cases where both "-ible" and "-able" can be used with the same word, often with slightly different meanings.