Learn Hardcore Greek: Θέλετε λίγο νερό;

Both. Θέλετε is the 2nd person plural of θέλω (to want). Greek also uses the plural as a polite form when addressing one person respectfully. Context tells you whether it’s plural “you all” or polite “you (sir/ma’am).”

What’s the informal singular version?

Use Θέλεις λίγο νερό; (standard) or the very common shortened form Θες λίγο νερό; Both mean the same; Θες is just more colloquial.

Is this closer to “Do you want” or “Would you like”? How can I make it more polite?

In offers, Greek often uses the present, so Θέλετε λίγο νερό; can sound like “Would you like some water?” To sound even softer/politer:

Θα θέλατε λίγο νερό; (literally “Would you like…?”)
Μήπως θέλετε λίγο νερό; (“Perhaps you’d like…?”)

Why is there a semicolon at the end?

In Greek, the symbol ; is the question mark. The high dot · (ano teleia) is the Greek semicolon.

Why is there no article before νερό? Could I say το νερό?

Mass/uncountable nouns in an indefinite sense normally drop the article. (Λίγο) νερό = “(some) water.” Το νερό means “the water” (a specific water already known). With λίγο, you almost never use an article.

What exactly is λίγο here? Does it change form?

Here λίγο is a quantifier meaning “a little (amount of).” It agrees with νερό (neuter, singular, accusative). The base adjective is λίγος/λίγη/λίγο (masc/fem/neuter). As an adverb, λίγο also means “a little, a bit,” e.g., Περιμένετε λίγο (“Wait a bit”).

What case is νερό in, and how does it decline?

Accusative singular (direct object of θέλω). Basic forms:

Singular: το νερό (nom/acc), του νερού (gen)
Plural: τα νερά (nom/acc), των νερών (gen)

Is the word order fixed? Could I say νερό λίγο?

Quantifiers/adjectives normally come before the noun, so λίγο νερό is the natural order. Νερό λίγο would sound odd unless used with special emphasis or in a very marked, contrastive context.

How do I pronounce the sentence?

Approximate IPA: [ˈθelete ˈliɣo neˈro]

Θ = th as in “think”
γ before o = a voiced fricative [ɣ] (a soft “gh”) in λίγο
ρ is a tapped/trilled r in νερό
Stress: ΘΈ-λε-τε, ΛÍ-γο, νε-ΡÓ
A rough guide: THEH-leh-teh LEE-gho ne-RO.

What are the accent marks doing?

They mark the stressed syllable of each word (one per word): stress falls on Θέ-, Λί-, and -ρό. Correct stress is essential for natural pronunciation.

How would I make it negative or ask “Don’t you want some water?”

Place δεν before the verb: Δεν θέλετε λίγο νερό; That’s “Don’t you want some water?” (often seeking confirmation). For a plain negative statement: Δεν θέλω νερό (“I don’t want water”).

What are other natural ways to offer water?

Να σας φέρω λίγο νερό; (“Shall I bring you some water?”)
Θα θέλατε λίγο νερό; (“Would you like some water?”)
Μήπως θέλετε λίγο νερό; (“Perhaps you’d like some water?”)

Can I use diminutives like νεράκι or λιγάκι?

Yes. Νεράκι (little water) is a friendly, very common way to refer to drinking water: Θέλετε νεράκι;
Λιγάκι is a diminutive of λίγο (“a tiny bit”), more casual: Θέλετε λιγάκι νερό; is possible, though λίγο νερό is more standard.

Can I drop λίγο or use ένα νερό?

Θέλετε νερό; is fine (more direct, neutral “Do you want water?”).
Θέλετε ένα νερό; means “Do you want a water?” i.e., one bottle/glass (common in cafés/restaurants).