Article: "the" or "a"

Please read the thread “sentences” where there is this sentence:

Both the speaker and the listener have known the year. (1)

Why there is “the” in front of “speaker” and “listener”? When I write:

Both a speaker and a listener have known the year. (2)

What is the difference in menaing btw (1) and (2)?You think I shoul write “the” or “a”?
What is the rule?



Look at the material I have written on the articles on this site:

ESL Lesson: Articles in English: The vs. A/an