"What is water?"
Translation:Hva er vann?
No, "vann" or water is not quantified. You don't say "en vann" in norwegian, it just won't make any sense. Same goes for "sand", "luft" and "melk".
And when you mean a bottle of water, can you say "en vann"? Like in "A pepsi and a water please!"
That's a good question. I think you can cuz it seems like an exception. In such a case you're a customer asking for a thing in a certain amount/quantity.
Yes, but then there's an implied "flaske" (bottle) in there, and that's what makes it countable. It would still be much more common to say "en flaske vann", though.
You can think of it with much and many. If you had 100g of water, would you say much water or many water? In this case, you would say much, so you don't use en.
"et" like "en" or "ei" (in front of a nomen) is like the english "a(n)", but gendered. "er" is the presens of the infinitiv "(å) være" meaning "to be".
"et" - indefinite article for nouns of neuter gender, "en" - indefinite article for nouns of masculine gender, "ei" - indefinite article for nouns of feminine gender. Also, "en" can be used instead of "ei" ("ei kvinne" and "en kvinne" are both correct).