Why do we use indefinite articles in sentences as follows:

John is a doctor.
Mary is training to be an engineer.
He wants to be a dancer.

  • because John's not the definitive doctor, Mary won't be the definitive Engineer and He won't be the definitive dancer. Commented Nov 22, 2013 at 21:18
  • 2
    John can't be the doctor, that's currently Matt Smith's job.
    – Jon Hanna
    Commented Nov 22, 2013 at 23:58
  • Because that's how English works. Sorry, but that is the whole of the answer. You can come up with explanations to account for it, but like nearly all "why" questions about languages, explanations are ex post facto rationalisations, and the answer is really "because that's how we do it".
    – Colin Fine
    Commented Nov 23, 2013 at 1:12
  • 1
    I suspect the question is asking why English requires the indefinite article here, whereas languages such as German and French don't: Er ist Arzt. Il est médecin.
    – Shoe
    Commented Nov 23, 2013 at 7:26
  • This question appears to be off-topic because it is probably suitable for English Language Learners
    – Kris
    Commented Nov 23, 2013 at 12:33

2 Answers 2


"John is a doctor" simply describes John's profession. "John is the Doctor" would require some antecedent, because it implies that he is someone that has been implicitly or explicitly mentioned before.

"I have two friends, a doctor and an engineer. They are coming tonight"

Then some time later...

"Oh, you remember that I was telling you of my two professional friends? John is the doctor."

"The", being a definite article, says that a mentioned thing is a particular instance of that thing. He's not just anyone with a medical degree, he's one I mentioned recently.


If you have a group of people who are doctors, John is an example of one of them, so "John is a doctor". Use of the definite article would imply you are identifying John as being the doctor among a group of people not all of whom are doctors, as Hack Saw says, or else focussing down on what John does that identifies him as one particular doctor or doing one particular job - "John is the doctor who covers night-shifts at the out-of-hours service".

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