Adjective or Adverb

The test is always: find the word being modified, then check what kind of word it is. If it's a noun or pronoun, you need an adjective. If it's a verb, an adjective, or another adverb, you need an adverb. 'She sings beautiful' fails because 'beautiful' is trying to describe the verb 'sings,' and adjectives can't do that job. 'She has a beautiful voice' works because 'beautiful' describes the noun 'voice,' which is exactly what adjectives are for.

This trips people up because of the -ly habit. Most adverbs are built by adding -ly to an adjective (quick → quickly, smooth → smoothly), so it's tempting to treat -ly as the whole rule. But some words are already adverbs in their plain form: 'fast' and 'hard' never take -ly as adverbs ('she ran fast,' not 'she ran fastly'). So the real question is never 'does this word end in -ly,' it's 'what is this word modifying.' The same logic stacks: when an adverb modifies another adverb, as in 'remarkably quickly,' the first word still has to be an adverb, because it's not describing a noun at all.

This connects to modifier placement because once you know a word is doing adverb work, it still has to sit next to the verb, adjective, or adverb it's modifying, not drift toward a noun it was never meant to touch. Misplaced modifiers and adjective/adverb mix-ups are really the same error at different stages: pick the right form first, then put it in the right spot.