-ly is a common suffix for adverbs, which modify verbs, adjectives, or other adverbs. Examples:
* slowly, quickly, happily
However, adjectives have many different endings, including:
* -ful (beautiful, helpful)
* -less (careless, hopeless)
* -ous (dangerous, famous)
* -y (happy, sleepy)
* -ic (fantastic, classic)
* -al (national, original)
And some adjectives have no special endings at all:
* good, bad, big, small, red, blue
So, while some adjectives end in -ly, this is not a universal rule. It's important to pay attention to the specific word and its function in a sentence to determine whether it is an adjective or an adverb.