The is the definite article. It points to one specific noun that the listener already knows which one is meant.
I closed the door, the door you and I both have in mind. Or The bus is late, the one you were waiting for.
Someone says:
I saw a dog in the yard.
A moment later:
The dog followed me to the gate.
The works here because the dog is now the one you both know about.
At home you might say, Please feed the cat. There is no need to say which cat, since your household has only one, and the listener knows exactly which animal is meant.
The is the definite article. It points to one specific noun that the listener already knows which one is meant.
I closed the door, the door you and I both have in mind. Or The bus is late, the one you were waiting for.
Someone says:
The tells your listener that one specific thing is meant, something they can already identify. If you say The dog followed me to the gate, your listener knows exactly which dog, because you had mentioned it earlier or it was the only dog in sight.
At home you might say, Please feed the cat. There is no need to say which cat, since your household has only one, and the listener knows exactly which animal is meant.
English has only one definite article, the, so nothing else competes for its job. A nearby point to keep things clear: the works with singular and plural nouns alike, as long as both people know which ones are meant. You can say the answer or the answers without changing the article.