The article depends on context.
If there is only one of the nouns that would apply to your situation, use "the." With public transportation, there are more than one, but you mean one of the buses that runs your route, one of the trains that goes to your destination, etc. when you use "the."
When my daughter wants to go to "the" mall, she means the one in the next town. But if you are not familiar with where you are, you might ask "Is there a mall nearby?" Any mall is fine.
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