I have been trying to ascertain the Spanish translation for the word "bookcase". I have been told it is "estantería", but when I look it up in Spanish-English dictionaries it mostly comes up as shelf. If I were in a kitchen that had a bookcase and I said to someone : "Puse la carta sobre la estantería", would they understand that I meant the bookcase or would I need to clarify? If a further clarification is needed then what would I need to say to clearly indicate that I meant the bookcase and not a shelf that had cookware on it?
A note about custom and usage:
If you see the little exchange between Marianne and me in the comments area of Marianne's post, you will get a fine example of the differences that come in play between "technically correct" language, and how a language is used on a daily basis on a given place.
Marianne learned one way to refer to an object, and in the cultural context where she learned, that's probably the common way to refer to the object.
I learned a different way - although I would understand perfectly is someone told me: "está sobre el estante". It so happens that the RAE dictionary agrees with the way I learned the word - but it does not mean that what Marianne learned is functionally wrong. People use language differently in different countries and regions, and that's why it is important to practice with the natives of an area, if you you really wish to fit with the flow on an informal conversation.
Estantería is basically a shelf. It can be a bookshelf, but it can be any other type of shelf.
If you want to make sure you are referring to a bookcase of a bookshelf, then you may want to say: "biblioteca", which by the way is the same word for "library".
I was under the impression that a shelf was "estante" and a bookcase was "estantería" (a set of shelves).
Let's wait and see what others have to say.
Edit Please see Gekkosan's answer!