The quick answer

Use a/an for one thing you mention for the first time, the for something specific or already known, and no article for general plural or uncountable nouns. Say I have a dog. The dog is friendly., not I have dog. Dog is friendly.

The rule

A/an introduces one thing for the first time: I saw a dog. Use an before a vowel sound, not just a vowel letter: an hour (silent h), a university (consonant /j/ sound). The refers back to something already mentioned, or something unique or specific: The dog followed me home., The Sun is bright today. Use no article for general statements with plural or uncountable nouns: Cats are independent., I love music., and for meals and some fixed expressions: We had dinner.

Form

Examples

• I saw a dog. The dog was friendly.
• She waited for an hour.
• I love music.
• We had dinner together.
• She is the best student in the class.

Common mistakes

• ❌ I have dog. → ✅ I have a dog. A singular countable noun always needs an article.
• ❌ She is a honest person. → ✅ She is an honest person. Use an before a vowel sound, even if the spelling starts with h.
• ❌ I love the music. → ✅ I love music. A general statement about music needs no article.
• ❌ Cats are the independent animals. → ✅ Cats are independent animals. A general statement about all cats needs no article.