Why do we use "the" with non-specific noun?

The best account of article usage I've ever read is in Quirk et al.'s Comprehensive Grammar. The book devotes dozens of pages to the topic, and addresses "the theater" and "the cinema" issues with skill.

This may not sound like a good answer (though, imho, it's the very answer): the thes are used in your examples even though the nouns are not specific because they're definite.

I would learn "to go to the theatre/the cinema" as idiomatic expressions and not try to explain them with rules.

2 Answers 2

In these sentences you are using "the" to refer to the category of a thing, and so to say "I don't like going to the theater" is the same as saying "I don't like going to theaters". It's a little confusing, but using the indefinite article in 'I do not like a theater' suggests that there is one theater that you do not like, but you might like other theaters.

You cannot construct sentences like this with any noun, so be careful. The first of these two sentences is fine, the second is not:

I do not like to travel on the bus.

I do not like to eat the sandwich.

'I do not like a theater' - from this sentence, is it like that i have already known which theater is in my mind but because of a listener doesn't know what in my mind, so I should use 'a' with the reason that not both of us known a specific place?

Yes, you would use a in this case because you know which theater you mean but the listener does not. However, although the sentence "I do not like a theater" is technically correct, it would sound unusual to most people. A much more natural way to phrase the same statement would be "there is a theater I do not like." To get specific, you might say "that is the theater I do not like."

If you considered the sandwich as referring to the prototypical sandwich then the sentence is indeed fine.