Trasa prowadzi głównie przez las.

Trasa means route, course, or trail, and here it is the subject of the sentence.

It is a feminine noun in Polish. You can often recognize feminine nouns because many of them end in -a, as trasa does.

That is why the verb is prowadzi rather than a masculine or plural form. In the present tense, Polish verbs agree with the subject, but in the 3rd person singular present, the form is often the same for masculine, feminine, and neuter subjects, so you just get prowadzi = leads / goes / runs.

Yes, prowadzi literally means leads, from the verb prowadzić.

But in Polish, just like in English, a route or path can metaphorically lead somewhere or run through somewhere. So:

• Trasa prowadzi przez las = The route goes/runs through the forest
• literally: The route leads through the forest

This is a very natural way to describe where a road, path, or route goes.

Głównie means mainly, mostly, or primarily.

In this sentence, it modifies the idea of the route’s course:

• Trasa prowadzi głównie przez las = The route mainly goes through the forest

Its position is natural and neutral. In Polish, adverbs like głównie are fairly flexible, but not every position sounds equally natural.

These are possible, for example:

• Trasa prowadzi głównie przez las — neutral, very natural
• Głównie trasa prowadzi przez las — unusual in most contexts
• Trasa głównie prowadzi przez las — possible, but less natural than the standard version

So the original word order is the best one to learn first.

Przez usually means through, across, or sometimes via, depending on context.

Here it means through:

• przez las = through the forest

It is used when something passes through an area, space, or obstacle. So if a route goes through a forest, przez is exactly the right preposition.

Because przez requires the accusative case.

The noun las is masculine singular. Its cases are:

• nominative: las
• accusative: las
• locative: lesie
• instrumental: lasem

After przez, you need the accusative, so:

• przez las = correct

Not:

• przez lesie — incorrect
• przez lasem — incorrect

A useful thing to remember is that for many masculine inanimate nouns, the accusative singular looks the same as the nominative singular. That is why it stays las.

They express different ideas:

• przez las = through the forest
  This focuses on movement from one side/part to another through the forest.

• w lesie = in the forest
  This focuses on location, not movement through it.

So:

• Trasa prowadzi przez las = the route goes through the forest
• Trasa jest w lesie = the route is in the forest

Both can be true, but they mean different things.

Polish does not have articles like a or the.

So las can mean:

• a forest
• the forest

The exact meaning depends on context.

In this sentence, English will often translate it as the forest because that sounds more natural in context:

• The route mainly goes through the forest

But grammatically, Polish itself does not mark that distinction with an article.

Yes, absolutely.

• Trasa prowadzi głównie przez las = The route mainly goes through the forest
• Ta trasa prowadzi głównie przez las = This route mainly goes through the forest

Adding ta makes it more specific. Without it, the sentence is more neutral and general.

A rough English-style guide would be:

TRA-sa pro-VA-djee GWOOV-nye pshehss las

A few important sounds:

• trasa → TRA-sa
• prowadzi → pro-VA-dzi
  • dz is pronounced together, like a voiced ts/dz sound
• głównie
  • ł sounds like English w
  • so it starts roughly like gw
• przez
  • rz here sounds like zh / sh-like Polish ż
  • the whole word is roughly pshez/pshehs, depending on speed and accent

If you want a more Polish-accurate breakdown:

• Trasa → TRA-sa
• prowadzi → pro-VA-dzi
• głównie → GWOOV-nye
• przez las → pshez las

Yes. That is exactly what głównie suggests.

• Trasa prowadzi przez las = the route goes through the forest
• Trasa prowadzi głównie przez las = the route goes mostly through the forest

So the route probably is not entirely in the forest. It may begin or end somewhere else, but most of it goes through wooded area.