Learn Romanian: Vreau puțină apă. - I want a little water.

In Romanian, the verb itself tells you who is doing the action. Vreau is the "I" form of the verb "to want", so you don't need to add the word for "I" (eu) unless you really want to emphasize it.

Why is it puțină instead of the base form puțin?

Words that describe quantities have to match the gender of the noun they go with. Since apă (water) is a feminine noun, the word for "a little" changes from its basic masculine form puțin to the feminine form puțină.

If I just want to say "I want some water," do I need to use puțină?

No. If you mean "some water" in a general sense, you can just say Vreau apă (literally "I want water"). You use puțină specifically when you want to make sure you only get a small amount.

How can I tell that apă is a feminine word?

A very helpful pattern for beginners is to look at the last letter of the word. Most Romanian singular nouns that end in the letter -ă (like apă) are feminine.