Which suffix is typically associated with forming adverbs?

The suffix that is typically associated with forming adverbs is -ly. When added to adjectives, this suffix transforms them into adverbs that describe how an action is performed. For instance, the adjective "quick" becomes "quickly," which tells us how someone does something (in this case, a quick manner). This transformation is a common and widely recognized pattern in English grammar.

Other suffixes have different functions. For example, -ful generally forms adjectives that convey a sense of being full of the quality indicated by the root word, such as "joyful." The suffix -able forms adjectives that suggest capability, as seen in "readable." Lastly, -est is typically used to form the superlative of adjectives, indicating the highest degree of a quality, such as "fastest." These suffixes do not serve the role of creating adverbs in the same way that -ly does.