David M. answered 03/27/19
Trained grammar instructor
One way to remember the difference between the two is that the definitive article (the) refers to a specific noun while indefinite articles (a, an,) refers to non-specific nouns. For example: "I want a pen." In this case the speaker will take any pen that's available. However, if the speaker says "I want the pen," then that changes the meaning because the speaker is looking for a specific pen. Hope that helps!