Differentiating between good and well is all well and good (Yes, I just did that.), but it can be a bit—shall I say nitpicky?—in informal settings. In formal ones, it’s another matter.
I perhaps should define what I mean by “formal.” I use the word to refer to newsrooms, blogs, and professional correspondence. In those situations, words matter. They show a person competent. They can make or break an article, pitch, or news story.
Good and well are words that differ in usage. The former is always an adjective. The latter almost always is an adverb.
To illustrate the point: I can have a good day. I may know a good dancer (I actually know a few.). My friend could be in good health. All the “good’s” in the previous sentences modify another word: day, dancer, and health.
Well typically answers the question “how.” How do my friends dance? They dance well.
Now for the tricky part. “Well” can act the part of the adjective when the word refers to health. For example, I can tell my healthy friend, “You look well.” If I say “good,” I am not saying the same thing; rather, I am saying I find my friend’s countenance pleasing. I very well might, but I find it good practice to be careful about making such statements.
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