If you guessed “not a good person,” then you are correct.

We can first simplify it by taking out the adjective good and then add a subject and verb to the phrase:

  • Incorrect: He is not person.
  • Correct: He is not a person.

The word person needs an article before it because it is a singular and countable noun even if there is an adjective like good in front of it:

  • Incorrect: He is not smart person.
  • Correct: He is not a smart person.
  • Incorrect: He is not good athlete.
  • Correct: He is not a good athlete.
  • Incorrect: He is great pianist.
  • Correct: He is a great pianist.

However, if you were just using good on its own without a noun following it, you would not need an article:

  • Incorrect: He is not a good.
  • Correct: He is not good.
  • Incorrect: He is a fast.
  • Correct: He is fast.

Here is a quick rule of thumb:

  • Incorrect: (Subject) is (singular noun).
  • Correct: (Subject) is a (singular noun).
  • Incorrect: (Subject) is a (adjective).
  • Correct: (Subject) is (adjective).

This rule of thumb applies even when there is an adjective or even multiple adjectives in front of the singular noun.

Below are some other examples you can refer to:

  • Incorrect: She is tall woman.
  • Correct: She is a tall woman.
  • Incorrect: She is a tall.
  • Correct: She is a tall woman.

  • Incorrect: Bob is wise man.
  • Correct: Bob is a wise man.
  • Incorrect: Bob is a wise.
  • Correct: Bob is wise.

  • Incorrect: Janice is rebellious student.
  • Correct: Janice is a rebellious student.
  • Incorrect: Janice is a rebellious.
  • Correct: Janice is rebellious.

So quick quiz: Which of the following is correct:

  • A: Paul is a renown screenwriter.
  • B: Paul is renown screenwriter.

If you answered A, then you’re absolutely right.

Screenwriter is a singular noun that requires an article before it even if it is preceded by the adjective renown.

If you still have trouble with knowing whether or not you should use an article in your sentence, check out our AI-powered online proofreader Pcanpi where you can input your sentences and get immediate feedback and suggestions.