English Grammar

Hello, DJ101. I love these kinds of questions, since they force me to think of language in a way that I often take for granted. In the above sentences, it is not as though the first sentence is necessarily incorrect, just that if the sentence means to convey that the object called chair is being held up as a representative of an entire group of such objects, then the article the is appropriate. By way of a parallel group of sentences, I think I can illustrate the point better:

1) A lion is the "king of the jungle."
Meaning: Some lion, perhaps not lions in general, is called the "king of the jungle."

2) The lion is the "king of the jungle."
Meaning: The animal known as lion is known as the "king of the jungle." Any lion qualifies.

Getting back to the chairs, the former sentence conveys that some chair, not necessarily a representative of all chairs, is a useful piece of furniture. I could utter that sentence right now in reference to the chair I am sitting in, but if we were speaking face to face, you would only look at my chair and either agree or disagree. You would not be thinking of the invention of the chair.

I could think of other examples to illustrate the point—e.g., A/The woolly mammoth went extinct...—but I hope what I have written above will satisfy your curiosity for now. Good luck with your studies.

- Andrew