Learn Hardcore Hungarian: Ebéd közben lassan vizet iszom.

Ebéd közben = during (the) lunch / while having lunch in a general way.
We are not talking about one specific, already-identified lunch; we’re just talking about the activity of having lunch.

You can say Az ebéd közben, but it would typically sound like:

during the lunch (that we both know about / that was mentioned before)

So:

Ebéd közben vizet iszom. ≈ I (generally) drink water during lunch.
Az ebéd közben vizet iszom. ≈ During that particular lunch, I drink water. (more specific, less common in isolation)

What exactly does közben mean here, and how is it different from alatt?

Közben literally means “in the meanwhile / while (something is happening)”.

Ebéd közben ≈ in the course of lunch, while (I’m) having lunch.

Contrast with alatt, which is a more neutral “during / under”:

Ebéd alatt also means during lunch, and is grammatically correct.
Ebéd közben tends to emphasize the time span of an ongoing activity: while lunch is happening.
Ebéd alatt sounds a bit more like a simple time frame: in the period of lunch.

In everyday speech, Ebéd közben is often preferred when you mean while I’m actually eating.

Why is Ebéd közben at the beginning? Can it go somewhere else?

Time expressions like Ebéd közben often come near the beginning of a Hungarian sentence, especially in neutral (non‑emphatic) sentences.

Your sentence:

Ebéd közben lassan vizet iszom.
→ Neutral: During lunch I slowly drink water.

You can move it, but the focus and rhythm may change:

Lassan vizet iszom ebéd közben.
→ Still correct; slightly more emphasis on how (slowly) and what (water), then you add when at the end.
Vizet iszom ebéd közben lassan.
→ Grammatically fine but sounds less natural; lassan is pushed to the end and can feel a bit tacked on.

For a basic, natural word order, time (Ebéd közben) near the start is a very good choice.

Why is it vizet and not víz? What does -et do?

Vizet is the accusative (object) form of víz (water).

víz = water (basic form)
vizet = water as a direct object → water in I drink water.

The ending -t marks the accusative case. Because víz has a front vowel (í), the language inserts -e- before -t to match vowel harmony:

víz → vizet (not vízt)

So:

vizet iszom = I drink water (literally: water-ACC I-drink).

Why is there no article before vizet? Why not a vizet iszom?

Hungarian usually drops the article for indefinite, uncountable, or “some” amounts of things, especially with food and drink:

Vizet iszom. ≈ I drink water / I’m drinking (some) water.
(Generic or unspecified quantity.)

If you say a vizet iszom, you are pointing to specific, known water:

A vizet iszom. ≈ I’m drinking the water (as opposed to something else).

Both are correct, but:

vizet iszom → some water / water in general
a vizet iszom → the particular water that we have in mind (often contrastive).

What is the function of lassan, and where can it go in the sentence?

Lassan means “slowly”; it’s an adverb describing how you drink.

In your sentence:

Ebéd közben lassan vizet iszom.
→ Neutral: During lunch I drink water slowly.

You can move lassan, with subtle changes:

Ebéd közben lassan vizet iszom.
– Neutral: time → manner → object → verb.
Ebéd közben vizet lassan iszom.
– Puts a bit more emphasis on how you drink the water (the slowness).
Lassan iszom vizet ebéd közben.
– Starts with manner; sounds like you want to stress slowly more.
Vizet lassan iszom ebéd közben.
– Emphasis often falls on vizet (water) as the important new piece of information, with lassan closely attached to the verb.

All of these are grammatically correct. For a default learner-friendly version, your original order is excellent.

Does the position of lassan change the meaning, or only the emphasis?

Primarily, it changes the emphasis (focus), not the core dictionary meaning:

Ebéd közben lassan vizet iszom.
→ Balanced, neutral: you’re simply stating what happens and how.
Ebéd közben vizet lassan iszom.
→ Feels more like you’re highlighting the way you drink the water (slowly), perhaps in contrast to other ways or other drinks.
Lassan vizet iszom ebéd közben.
→ You lead with slowly, so it sounds like The important thing is that I do it slowly (during lunch).

In normal conversation, these differences are mostly subtle. Context and intonation decide whether something sounds contrastive or just stylistically varied.

Why is the verb iszom and not iszik or iszok?

The verb is inni (to drink), and it’s irregular. Present tense:

én iszom – I drink
te iszol – you drink
ő iszik – he/she drinks

So:

iszik is the 3rd person singular form (he/she drinks), so it would be wrong for I drink.
iszom is the standard 1st person singular form.

What about iszok?

iszok is a very common colloquial 1st person form.
In standard/educated written Hungarian, iszom is preferred.
In everyday speech, you will hear both; iszom never sounds wrong, iszok is just more informal.

Does iszom mean “I drink” or “I am drinking”? How do you say the continuous aspect?

Hungarian does not distinguish between “I drink” and “I am drinking” in the verb form. Iszom can mean either, depending on context:

Mindig vizet iszom ebéd közben.
→ I always drink water during lunch. (habitual)
Most ebéd közben vizet iszom.
→ Right now I am drinking water during lunch. (current action)

So:

iszom = I drink and I am drinking.
Continuous / progressive aspect is expressed by context words like most (now), éppen (just now), etc., not by changing the verb ending.

Can I say Ebéd közben lassan vizet iszok instead? Is it wrong?

It’s not wrong in spoken Hungarian, but you should know the nuance:

Ebéd közben lassan vizet iszom.
→ Standard 1st person form; good in writing and speech.
Ebéd közben lassan vizet iszok.
→ Colloquial; very common in everyday speech, less ideal in formal writing or exams.

If you are aiming for correct textbook Hungarian, use iszom.
If you’re imitating casual speech, iszok will sound natural and native-like.

Could I express the same idea with a clause like Miközben ebédelek, lassan vizet iszom? Is it equivalent?

Yes, that’s a very natural alternative:

Miközben ebédelek, lassan vizet iszom.
≈ While I’m having lunch, I slowly drink water.

Comparison:

Ebéd közben lassan vizet iszom.
– Uses a noun + postposition construction (ebéd közben) meaning during lunch.
Miközben ebédelek, lassan vizet iszom.
– Uses a subordinate clause with miközben (while) and a verb (ebédelek = I am having lunch).

Both are grammatically correct and natural. The ebéd közben version is slightly more compact; the miközben ebédelek version spells out the action of eating more explicitly.

Is there a difference between Ebéd közben lassan vizet iszom and Ebéd közben vizet iszom lassan?

Both are grammatically correct, but they sound different:

Ebéd közben lassan vizet iszom.
- Feels like the neutral sentence.
- Time (Ebéd közben) → manner (lassan) → object (vizet) → verb (iszom).
Ebéd közben vizet iszom lassan.
- Puts lassan at the end, which can feel slightly marked or stylistic.
- In spoken Hungarian, this might sound like you’re adding slowly as an afterthought, or giving it slight extra emphasis.

Neither is “wrong”, but for clear, standard word order, Ebéd közben lassan vizet iszom is the safer and more typical choice.