Articles: A, An, and The

“A/An” articles are called “Indefinite” because they are:  not specific, new or unknown to your listener:

  1. I need a new phone. (not a specific phone, just any phone)
  2. Linda is an arquitect. (new to the listener you are speaking to)
  3. You will find a tour guide somewhere. (unknown to the listener)

“The” articles are “definite” or specific articles. They are known to the listener:

  1. The sushi at the restaurant you recommended was fantastic. (known to listener)
  2. I prefer the blue car, not the red one. (specific)