When you use the article "the" you are referring to one specific thing (table, balcony, roof, etc.) Let's imagine you are in a classroom and there are 15 desks. If you say "put it on a desk" it means that I can put the objet in any desk. If you say "put it on the desk" you'd be talking about a specific desk which I'd be able to recognize by the rest of the contex of our conversation. So, using a word from your list: I traveled to another country and I was visiting A museum when the accident happended. (Maybe I don't remember the museum I was in, or knowing that it was a specific museum isn't as important) -Have you visited the National Art Museum? -Yes! Actually I met a friend when I was visiting THE museum. (I know the particular museum that was visited )

https://www.youtube.com/watch?v=ul1QI5-R6fA Please watch this video.

2. a(n) or the or zero article? Seeing the native speakers have given perfect explanation of the usage 'a(n)' and 'the', I'll add only a little more information on it. 1) 'the' used to show opposite or contrary relationship: the elements or parts are independant or opposite to each other while closely connected within a certain system. -- the mother/father and the son/daughter -- the top and bottom -- the head, the arms, the leges -- the parts and the whole -- the Sun, the Moon, the Earth; ( compare: Mars, Venus ) 2) zero article used with singular countable nouns,such 'as at school', 'at home', 'at work', 'at university' These uses indicate that you're not talking about the specific entities,but about their attributes,properties,features etc. at school -- you're studying, not working,regardless of which school you're studying in at university -- you're studying and you're not an elementary or high school student 3) occasionally it's optional to use either a(n) or the, or use either an article or zero article, with little meaning difference between.

A Little Essay on English Articles ------- For Answering an English Learner's Questions https://www.italki.com/question/405617 The little part of speech 'article'of English may be a great tricky problem to those whose native languages have no this class of words. For those whose native languages have neither the grammatical categoris of number,case,nor gender, these,especially the gender, may feel totally redundant burdens only to make troubles. But no. For the native speakers,they play significant roles in the grammar and the information communication. The Articles of English, as we'll discuss in this tiny essay, along with the number of nouns and the proceding prepositions, can convey varied subtle meanings. 1. on the list OR in the list? Both are correct. Sometimes, to express to basically the same meaning, you may have tow options, although there may be some fine nuances between the diffent collacations. -- on the list: in the list -- on the bed:in the bed -- on the street: in the street -- on holidy -- not at work or school -- during the holidays -- somebody to be doing sothing or something to be happening in the fairly long time -- in the holidays -- to do something or something to happen in the fairly long tome Needless to say, some nouns are used with different prepositons to show different meanings. -- at the festival -- on the occasion of the festival -- during/in the festival -- in the period of time of the festival -- to spend a week at a summer camp: your are spending the time around the camp,not always being staying in the camp -- to spead five years in a prison camp: you are confined in the camp,not allowed to leave Sometimes a noun would be used with a prepositon which do not unusally come together with it, but everyone will feel the use is natural because it closely fits the context.

Paul is quite right. I don't think there is ever a case of it being to do with the noun. It is only ever about the uniqueness of the item that you are referring to.