I saw a famous actor on the street yesterday!

[GeneD]

I saw a famous actor on the street yesterday! It's from here: http://www.englishcurrent.com/exercises/study-articles-exercises-online/

I actually put the correct article in the exercise (at least, it is marked as correct), but I can't explain why it is used there and not an indefinite article. We don't know exactly which street it could be. What do you think of it?

 

[Tarheel]

I guess it's an exception to the rule. I don't really have an answer to your "why" question. I do know that if said "I saw a famous actor on the street" it would mean I saw that person outside in a public place.

 

[GeneD]

I do know that if said "I saw a famous actor on the street" it would mean I saw that person outside in a public place.

It seems to be that "on the street" has a general meaning, right? I've googled "on the street" and come across a TV show named "Billy on the street" (which is pretty funny, by the way). https://www.youtube.com/watch?v=JYISejAY36s

He's living on/in the street. He's homeless.
He was going down the street when he met his friend.

It looks similar to "playing the piano" in which the generalization is made with the help of "the".

 

[Tarheel]

Yes, I think you have the right idea.