What is the major difference between 层 and 楼？ I know that 层 can refer to other things like layers, etc. but I've heard that it could also refer to floors (just like 楼）。 Could I say something like "酒吧的第一层？“
1 . When we put 层 and 楼 together and an ordinal number before them, they form a noun phrase meaning
This usage can be shortened into 第三层, 三层 or 三楼 (but not 第三楼). (第)三层 is fine for both formal and informal situations, while 三楼 sounds colloquial, otherwise they are completely interchangeable:
2 . When we put 层 and 楼 together and a cardinal number before them, they form a noun phrase meaning
Usages like this can be shortened into 三层, but not 三楼. E.g.
Examples for 三层高 (adj. phrase):
If the subject of the sentence is literally '楼', then it must not be repeated. E.g. replacing '酒吧' and '建筑' with '楼' in above examples:
Back to your question,
Could I say something like "酒吧的第一层？“
Yes. It means 'the first floor of the bar (which sounds like a multi-story building or occupies more than one floors in a building)'.
Yes you can, but it doesn't make sense. It seems like you are trying to say "The first floor of the bar?". Are you trying to say:
Hope it helps!
You might need to understand the mean of 層 and 樓.
樓 is a multi-storey building, usually wider than 塔. It is usually more than two floors. 樓 was rare in ancient China. There are some mentioned in poems like 岳陽樓 and 黃鶴樓.
層 is a storey of 樓 or 塔 and sometimes we say 層樓 or 一層樓. In an ancient poem, there are two lines of 欲窮千里目、更上一層樓.
When we counts storeys, we say 第一層, 第二層 and so on. Or 樓高六層.
The concept of 樓 for storey might be corrupted from 層樓. It is say 一樓, 二樓, 三樓 for location of floor.
You say "酒吧的第一層" is correct.