* The "le" is dropped: This is the common rule for forming adverbs.
* "Ly" is added: This creates the adverb suffix.
Examples:
* Gentle becomes gently
* Simple becomes simply
* Possible becomes possibly
* Terrible becomes terribly
Exceptions:
* Words ending in "ile": These words usually don't follow the rule, and you would add "ly" directly, for example, "agile" becomes "agility."
* Words ending in "cle": These words may or may not follow the rule, but generally do, such as "uncle" becomes "unklely."
Note: Some words ending in "le" can already be adverbs, in which case adding "ly" would create a strange or unnecessary word.