What part of speech frequently ends with -ly?

The correct choice is adverb because adverbs often modify verbs, adjectives, or other adverbs and frequently end with the suffix -ly. This morphological pattern allows for the identification of an adverb in a sentence, as they describe how, when, where, or to what extent an action is performed.

For example, words like quickly, smoothly, and happily are adverbs that indicate the manner in which something is done. While some adjectives can also end in -ly, the distinction is clear; the -ly suffix is primarily a marker for adverbs in the English language. Understanding this form can help one recognize adverbs in various contexts, aiding in both comprehension and effective use of language.