Niech on wstanie wcześniej, bo autobus zaraz odjeżdża.

Niech is used to make a kind of third-person command, suggestion, or wish. English does not have a simple imperative for he/she/they, so Polish uses niech.

So:

• Niech on wstanie wcześniej = Let him get up earlier / He should get up earlier

This pattern is very common:

• Niech przyjdzie = Let him/her come
• Niech zrobią to jutro = Let them do it tomorrow

It can sound like a request, instruction, or recommendation, depending on context.

Because after niech, Polish uses a finite verb form, not the infinitive.

• wstać = infinitive, to get up
• wstanie = he will get up / the 3rd person singular form of the perfective verb

So:

• Niech on wstanie = correct
• Niech on wstać = incorrect

With niech, you normally say:

• Niech zrobi
• Niech pójdzie
• Niech wstanie

not the infinitive.

This is mainly about aspect.

• wstać is perfective: a completed action, to get up
• wstawać / wstaje is imperfective: repeated or ongoing action, to be getting up / to get up habitually

In this sentence, the speaker means one concrete action: he needs to get up now, in time for the bus. That is why wstanie fits.

Compare:

• Niech wstanie wcześniej = Let him get up earlier this time
• Niech wstaje wcześniej = Let him get up earlier in general / as a habit

So the sentence uses the form that fits a single completed action.

Yes, it can absolutely be omitted.

Polish often leaves out subject pronouns, because the verb ending already shows the person. So:

• Niech on wstanie wcześniej
• Niech wstanie wcześniej

Both are grammatical.

Usually, Niech wstanie wcześniej sounds more natural unless you want to emphasize on:

• maybe to contrast him with someone else
• maybe to stress he, not someone else

So on is not necessary here; it adds emphasis.

Wcześniej means earlier.

It is related to wcześnie = early, but wcześniej is the form used when comparing with some expected or usual time:

• wstać wcześnie = to get up early
• wstać wcześniej = to get up earlier

In this sentence, it means he should get up earlier than planned / earlier than usual / earlier than would otherwise be necessary.

You do not need an explicit comparison word in the sentence. Polish often leaves that understood from context.

Because bo introduces a clause giving the reason.

• Niech on wstanie wcześniej, bo autobus zaraz odjeżdża.

In Polish, a comma before bo is standard. The second part explains why he should get up earlier.

So the structure is:

• statement/request + , bo
  • reason

This is normal Polish punctuation.

Both can mean because, but they differ in style.

• bo = common, natural, everyday
• ponieważ = more formal, more written, sometimes more careful in tone

So in everyday speech, bo is very natural here:

• Niech wstanie wcześniej, bo autobus zaraz odjeżdża.

A version with ponieważ is possible, but it sounds more formal:

• Niech wstanie wcześniej, ponieważ autobus zaraz odjeżdża.

Because Polish often uses the present tense for a scheduled or imminent future event, especially with verbs like departures, arrivals, timetables, and plans.

So:

• autobus zaraz odjeżdża = the bus is leaving very soon

This is very natural Polish.

English does something similar:

• The bus leaves in a minute
• The train is leaving soon

So even though the event is in the near future, the Polish present tense works perfectly here.

Yes, that is also possible.

There is a subtle difference:

• zaraz odjeżdża = the bus is just about to leave / it is departing very soon, often sounding like a scheduled or already unfolding situation
• zaraz odjedzie = the bus will leave very soon, with a bit more focus on the one future completed event

Both are natural. In everyday speech, zaraz odjeżdża is very common for transport.

Here zaraz means very soon, in a moment, or any minute now.

So:

• autobus zaraz odjeżdża = the bus is leaving very soon

Be careful: zaraz can have slightly different shades depending on context. It can mean:

• in a moment
• right away
• sometimes, in certain contexts, almost just now

But in this sentence, the meaning is clearly very soon.

No, Polish word order is fairly flexible, but different orders change the emphasis.

The given sentence is natural and neutral:

• Niech on wstanie wcześniej, bo autobus zaraz odjeżdża.

Other orders are possible, for example:

• Niech wcześniej wstanie, bo autobus zaraz odjeżdża.
  This puts more emphasis on wcześniej.

• Bo autobus zaraz odjeżdża, niech on wstanie wcześniej.
  This is possible, but less neutral in everyday use.

So the original order is a good standard version.

Not exactly in the same way as Wstań wcześniej! would be.

• Wstań wcześniej! = direct command to you
• Niech on wstanie wcześniej = indirect command/suggestion about him

So it is more like:

• Let him get up earlier
• He should get up earlier

It often sounds a bit less direct than a normal imperative, because the speaker is not addressing him directly, but speaking about what he should do.