When refer something immediately after it, should I use "a" or "the"?

Question

I guess I understand the basic rules of "A/an and the" in Cambridge Dictionary grammar tutorial.

However, I have no idea which rule in that tutorial fits the following situation.

A post use article "the" in this way

A research paper uses the term "proxy data sets" in this way

where "the term" refers to "proxy data sets" immediately after it. In this situation, should I use "a" or "the"?

Could someone please give a hint? Thanks in advance.

Answer 1

There is only one term "proxy data sets". There isn't another term that is also "proxy data sets" (like there is only one number 17. There aren't two different numbers among all the numbers we know that are both 17).

So when we talk about "proxy data sets", it's the term "proxy data sets". It's not (*)a term "proxy data sets" because if we're talking about "proxy data sets" as a term, there's no other term we could be talking about.

On the other hand, as I mentioned in comments, if we re-word the example a bit, we can end up using the indefinite article instead, as in

Jones' paper used a term, "proxy data sets", in a way that was new to me

In this example, what's important is that the paper used a term that was new to me (it could be any term at all). But then we've added an aside, mentioning what term that was. But just because we mentioned the term in passing doesn't change the overall sense that what was important that I learned a new term when reading the paper, rather than what term it was in particular.

Answer 2

@ThePhoton gave a good answer that I upvoted, but let me add a little to it.

In general, you use "the" when there is only one of the thing that you can be referring to, when taken in context. Use "a" when there is more than one.

Like, "I ate at a house on Elm Street." There are many houses on Elm Street. I visited one of the many. But, "I visited the house that Bob lives in." Bob presumably lives in only one house, so there's only one house that I can be talking about.

Sometimes either "a" or "the" is grammatically possible, but which you use depends on the facts. Like, "I got lunch in a diner in Cooperton" or "I got lunch in the diner in Cooperton"? If there is only one diner in Cooperton, then it should be "the". If there are two or more, it should be "a".

Whether something is "a" or "the" can change as the narrative proceeds. Often something is introduced as "a" because it is one of many. But once you have mentioned it, now it is the only one in the current context, so it becomes "the". For example, "In the bookstore, I found a book about aardvarks. I bought the book and found it fascinating." When I first mention this book, it is "a", because there are many books in the bookstore, maybe even many books about aardvarks, and this is one of the many. But once I focus attention on this book, now it becomes "the book", that is, the one book that I am now talking about.

Answer 3

I realize this has been answered, but I want to offer perhaps a simpler explanation:

• "A" is an indefinite article. It could be referencing any among several possible items, such as "a puppy," or "a color."
• "The" is a definite article. It references a specific item among a set of alternatives, or perhaps the only possible item in a given context.

In the context of your example, the writing is referring to a single, specific term of "proxy data sets;" hence, the definite article "the" is appropriate.