Learn Hardcore Polish: Nie wiem, czy on będzie na spotkaniu. - I don’t know whether he will be at the meeting.

Use czy when you report a yes/no question after verbs like wiedzieć (to know), pytać (to ask), zastanawiać się (to wonder), etc.
- Zastanawiam się, czy on przyjdzie. – I wonder if he will come.
Do not use czy for “if = in case / on condition that”. For that you use jeśli / jeżeli:
- Jeśli przyjdzie, zaczniemy. – If he comes, we’ll start.

Why is there a comma before czy?

In Polish, czy here introduces a subordinate clause (czy on będzie na spotkaniu), so a comma is required between the main clause and the subordinate clause:

Main clause: Nie wiem (I don’t know)
Subordinate clause: czy on będzie na spotkaniu (whether he will be at the meeting)

Polish punctuation rule: you normally separate subordinate clauses with a comma, so:

Nie wiem, czy on będzie na spotkaniu. ✅
Writing it without the comma is considered a mistake in standard Polish.

Do I really need the pronoun on, or can I say “Nie wiem, czy będzie na spotkaniu”?

You can absolutely omit on:

Nie wiem, czy będzie na spotkaniu. ✅
Nie wiem, czy on będzie na spotkaniu. ✅

Polish is a pro‑drop language: subject pronouns are often left out because the verb form already shows the person.

So why use on at all?

Without on: neutral, the identity is usually clear from context.
With on: can add emphasis or contrast:
- Nie wiem, czy on będzie na spotkaniu (as opposed to someone else).
- Or when you’re introducing or reminding who you mean.

In isolation, both versions are correct and natural; the one without on is slightly more common in neutral context.

Why is the verb będzie used, and what tense is it?

Będzie is 3rd person singular future of być (to be):

on będzie = he will be

So:

Nie wiem, czy on będzie na spotkaniu.
Literally: I don’t know whether he will be at the meeting.

Conjugation of być (future, singular):

ja będę – I will be
ty będziesz – you (sg) will be
on / ona / ono będzie – he / she / it will be

If you wanted present tense (“I don’t know if he is at the meeting (now)”), you’d say:

Nie wiem, czy on jest na spotkaniu. – I don’t know if he is at the meeting.

Why is it na spotkaniu, not na spotkanie?

Because na here means “at” and requires the locative case, not the accusative:

na
- locative = at / on (location)
  - na spotkaniu – at the meeting
  - na stadionie – at the stadium
  - na poczcie – at the post office

So:

Nie wiem, czy on będzie na spotkaniu.
= I don’t know if he will be at the meeting.

Na spotkanie (accusative) is used mainly for movement towards something:

Idę na spotkanie. – I’m going to the meeting.
Zaprosiłem go na spotkanie. – I invited him to a meeting.

So:

będzie na spotkaniu – will be at the meeting (location)
idzie na spotkanie – is going to the meeting (direction)

Why is it spotkaniu and not spotkanie after na?

Because of case inflection.
The noun spotkanie (a meeting) is neuter, singular:

Nominative: spotkanie – (this) meeting
Locative: spotkaniu – at (this) meeting

With na expressing location, you need locative:

na spotkaniu – at the meeting ✅
na spotkanie – only in meanings with motion to a meeting (accusative)

So the change from -e to -u is the locative ending for many neuter nouns:

muzeum → w muzeum (in the museum)
mieszkanie → w mieszkaniu (in the flat)
spotkanie → na spotkaniu (at the meeting)

Why is it na spotkaniu and not w spotkaniu?

In Polish, for events like meetings, concerts, lessons, etc., the natural preposition for “at (an event)” is usually na:

na spotkaniu – at a meeting
na koncercie – at a concert
na lekcji – at a lesson
na konferencji – at a conference

W spotkaniu is only correct in certain expressions and usually combined with another verb:

brać udział w spotkaniu – to take part in a meeting
uczestniczyć w spotkaniu – to participate in a meeting

But on its own, for simple “be at the meeting”, you say:

być na spotkaniu – to be at a meeting ✅
not być w spotkaniu ❌

What’s the difference between “Nie wiem, czy on będzie na spotkaniu” and “Nie wiem, czy on jest na spotkaniu”?

The difference is time reference:

Nie wiem, czy on będzie na spotkaniu.
- Future: “I don’t know if he will be at the meeting (later / tomorrow / in the future).”
Nie wiem, czy on jest na spotkaniu.
- Present: “I don’t know if he is at the meeting (now / currently).”

English sometimes uses present tense for scheduled future events (“I don’t know if he is at the meeting tomorrow”), but Polish is stricter:

For future events, you normally use future tense (będzie).
For what might be happening right now, use present (jest).

Is there any difference in meaning if I change the word order in the second part, e.g. “czy będzie on na spotkaniu” or “czy on na spotkaniu będzie”?

All of these are grammatically correct, but differ in naturalness and emphasis:

czy on będzie na spotkaniu – the most neutral and natural order. ✅
czy będzie on na spotkaniu – possible, but sounds a bit marked; can give extra emphasis to on (like “whether HE will be at the meeting”).
czy on na spotkaniu będzie – also possible; you’re slightly emphasizing “at the meeting” or contrasting it with some other place.

In everyday speech and writing, “czy on będzie na spotkaniu” (or without on) is by far the most typical choice.

Could I say “Nie znam, czy on będzie na spotkaniu” instead of “Nie wiem”?

No, that would be incorrect.

znać means “to know (be familiar with) someone or something”:
- Znam go. – I know him.
- Znam to miasto. – I know this city.

You can’t use znać with an entire clause like “czy on będzie na spotkaniu”.

For knowing facts, answers, or information expressed in a clause, you must use wiedzieć:

Nie wiem, czy on będzie na spotkaniu. ✅
(I don’t know whether he will be at the meeting.)

So:

znać – to know (be acquainted with) a person / place / thing
wiedzieć – to know a fact / information / clause (often followed by że or czy)