I did well.
I did good.
Which one is a correct sentence? Please explain it with reasons. Can you please define them?
Both sentences can be correct, but they have a different meaning.
In the first sentence, well is an adverb that modifies did. Well is the adverbial form of good, and in this case it means that what the speaker did, he did in a good way, with good results. When writing sentences like this, ensure that you know which word is being modified. If it modifies a noun, an adjective is used while an adverb is used to modify verbs or adjectives:
A good man.
The word good modifies the noun man which requires it to be in its adjective form. In your sentence it modifies the verb and is in the adverbial form:
I did well.
Now, this might make you think that your second sentence is wrong, but it is not. It does, however, have a different meaning than the first sentence. In that second sentence, good is used as a noun. It cannot be used as an adjective because there is no noun next to it to be modified nor is there a copular verb which could link it to the subject. The phrase do good is used in the meaning of be benificial, aid. It is often used with a direct object, the person or object that benefits or receives the aid. Here's an example with the phrase to do someone good:
- A: I'm feeling sick.
- B: Drink some tea, it will do you good.
You can see how this meaning is very different from your first sentence. You can do well on an exam, but you can't do good on it. You can, however, do good by helping someone else.
Only the following version is considered grammatically correct:
I did well on the test.
The reason being is that well is an adverb modifying the verb did. You use adverbs to make your verbs sound more colorful. That's their primary function.
However, many Americans do say:
I did pretty good on the test.
which is, of course, grammatically incorrect because good is an adjective. Adjectives are only used to modify nouns. So, what we have here is called a colloquialism—something that's accepted in spoken language because of its widespread use despite the fact that it's grammatically wrong. I have an American teacher who himself many times uses good instead of the proper form well which only goes to show how extremely common it has become to say good instead of well in daily English. But, I bet ya, when he has to write something like a business letter or simply send a notification message to his students, he's definitely going to use the proper form well.
So, my recommendations: