"What is water?"
Translation:Hva er vann?
- 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 (both ei kvinne and en kvinne are correct).
Water in Norwegian is et vann (neuter gender) but this implies that it's countable which it isn't (you can't say one water, two waters etc.) so the indefinite article is omitted.
Definite singular is vannet (the water).