adjectives, adverbs, modifier confusion
"If I hit a bad shot, people five fairways away know it because I'm yelling [his favorite curse word], but if I hit a good shot, I'm yelling too. Everybody knows the difference in the yelling. Either Sam is playing well, or he's playing bad." - Samuel L. Jackson, in People, about his behavior on the golf course
Samuel has made an error in modifier confusion: he has used an adjective to modify a verb. Only an adverb can modify a verb.
In the last sentence, the second instance of the verb "playing" is modified by the adjective "bad." This is incorrect because an adjective cannot modify a verb. To correct the error, replace the adjective with an adverb.
"Either Sam is playing well, or he's playing badly."
"Either Sam is playing well, or he's playing poorly."
