Na ferie jedziemy w góry, jeśli dzieci nie będą chore.

Ferie usually means school holidays / school break, especially the winter break in Poland.

A useful thing to know: ferie is normally used only in the plural. So Polish says:

• ferie są = the holidays are
• na ferie = for the holidays
• w ferie = during the holidays

For summer holidays, Polish more often uses wakacje.

Because na and w mean different things here.

• na ferie = for the holidays / for the holiday period
• w ferie = during the holidays

So in this sentence, Na ferie jedziemy w góry means the trip is planned for the holiday break.

This is a very common pattern in Polish:

• na wakacje = for the vacation
• na weekend = for the weekend
• na urlop = for vacation / on leave

Because Polish often uses the present tense to talk about a planned future event, especially with verbs of motion.

So jedziemy here works a lot like English:

• We’re going to the mountains...

not just

• We go to the mountains...

This use sounds natural when the plan is already arranged or expected.

Yes, absolutely.

• jedziemy = we’re going, we’re planning to go
• pojedziemy = we will go

Both are possible, but the nuance is slightly different:

• jedziemy sounds more like an arranged plan
• pojedziemy sounds like a straightforward future fact

So these are both natural:

• Na ferie jedziemy w góry...
• Na ferie pojedziemy w góry...

Because Polish distinguishes different kinds of going more clearly than English does.

• iść / idziemy = go on foot, walk
• jechać / jedziemy = go by vehicle, travel by car/train/bus/etc.

A trip to the mountains for the holidays is normally understood as travel by some vehicle, so jedziemy is the natural choice.

In Polish, w góry is the normal expression for to the mountains.

Two important points:

1. w

   • accusative is used here because there is movement toward a destination
   • jedziemy w góry = we’re going to the mountains

2. Polish normally uses góry in the plural for this idea

   • w góry = to the mountains
   • w górach = in the mountains

So compare:

• Jedziemy w góry. = We’re going to the mountains.
• Jesteśmy w górach. = We’re in the mountains.

Because Polish word order is quite flexible, and the speaker can move parts of the sentence to the front for emphasis or for context.

Starting with Na ferie sets the time frame immediately:

• Na ferie jedziemy w góry... = As for the holidays, we’re going to the mountains...

A more neutral order could also be:

• Jedziemy w góry na ferie, jeśli dzieci nie będą chore.

Both are correct. The original just highlights the holiday period first.

Because jeśli introduces a subordinate clause in Polish, and such clauses are normally separated by a comma.

So:

• Na ferie jedziemy w góry, jeśli dzieci nie będą chore.

If the jeśli clause comes first, the comma still appears, just in the other place:

• Jeśli dzieci nie będą chore, jedziemy w góry na ferie.

Because dzieci is the irregular plural of dziecko.

• dziecko = child
• dzieci = children

In this sentence, dzieci is the subject, so it is in the nominative plural.

This is a very common word pair and just has to be learned as an irregular form.

Because Polish is using the future of to be plus an adjective:

• będą = they will be
• chore = sick

So:

• dzieci nie będą chore = the children will not be sick

Why chore?

Because the adjective has to agree with dzieci.
Dzieci takes the non-masculine-personal plural adjective form, so you get:

• chore = sick, plural form used with dzieci

Compare:

• dziecko jest chore = the child is sick
• dzieci są chore = the children are sick
• dzieci nie będą chore = the children will not be sick

So the ending is there because of agreement with dzieci.