As we’ve learned, adjectives and adverbs act in similar but different roles. A lot of the time this difference can be seen in the structure of the words:

• A clever new idea.
• A cleverly developed idea.

Clever is an adjective, and cleverly is an adverb. This adjective + ly construction is a short-cut to identifying adverbs.

https://youtu.be/b4KybdSi1Fc

While –ly is helpful, it’s not a universal rule. Not all words that end in –ly are adverbs: lovely, costly, friendly, etc. Additionally, not all adverbs end in -ly: here, there, together, yesterday, aboard, very, almost, etc.

Some words can function both as an adjective and as and adverb:

• Fast is an adjective in “a fast car” (where it qualifies the noun car), but an adverb in “he drove fast” (where it modifies the verb drove).
• Likely is an adjective in “a likely outcome” (where it modifies the noun outcome), but an adverb in “we will likely go” (where it modifies the verb go).