How are most adjectives changed into adverbs?

Most adjectives are changed into adverbs by adding the suffix "-ly" to the end of the adjective. For example, "quick" becomes "quickly," and "happy" turns into "happily." However, some adjectives that already end in "-ly," such as "friendly," do not change form when used as adverbs. Additionally, some adverbs are irregular and do not follow this pattern, like "good," which changes to "well."