Teren pasieki jest duży.

Because pasieki is the genitive singular form of pasieka.

In Polish, when one noun depends on another, the second noun is often put in the genitive case. Here:

• teren = area, ground, terrain
• pasieka = apiary
• teren pasieki = the area/grounds of the apiary

So pasieki means of the apiary, not just apiary.

Teren is in the nominative singular because it is the subject of the sentence.

The sentence structure is:

• Teren pasieki = the apiary grounds / the area of the apiary
• jest = is
• duży = large

So teren is the thing being described.

Because duży has to agree with teren, and teren is:

• masculine
• singular
• nominative

So the adjective must also be masculine singular nominative:

• duży for masculine
• duża for feminine
• duże for neuter

Even though pasieka is feminine, the adjective does not agree with pasieka here. It agrees with teren, because teren is the main noun being described.

In a normal, complete sentence like this, jest is standard and natural.

• Teren pasieki jest duży. = normal everyday sentence

Polish sometimes omits jest in very informal speech, notes, headlines, or poetic style, but in ordinary standard Polish, keeping jest is the best choice here.

So for a learner, it is safest to treat jest as necessary in this sentence.

The basic word order here is very natural:

• Teren pasieki jest duży.

Polish word order is more flexible than English, but changes usually add emphasis or change the focus.

For example:

• Duży jest teren pasieki. = emphasizes large
• Teren pasieki jest duży. = neutral statement

However, the noun phrase teren pasieki normally stays together, because pasieki depends on teren.

Because Polish does not have articles like a or the.

So:

• teren can mean an area, the area, or just area, depending on context
• teren pasieki can mean the area of the apiary or apiary grounds

Polish relies on context instead of articles.

Here, teren means something like:

• area
• grounds
• site
• land/space

In this sentence, teren pasieki is most naturally understood as the grounds of the apiary or the apiary area.

It does not usually mean just abstract terrain here. It refers more to the physical area belonging to or used by the apiary.

The dictionary forms are:

• teren → already in dictionary form
• pasieki → dictionary form is pasieka
• jest → dictionary form is być (to be)
• duży → already in dictionary form

So the sentence is built from:

• teren
• pasieka
• być
• duży

A rough pronunciation guide is:

• Teren ≈ TEH-ren
• pasieki ≈ pa-SYEH-kee
• jest ≈ yest
• duży ≈ DOO-zhih

A fuller approximation:

TEH-ren pa-SYEH-kee yest DOO-zhih

A few helpful sound notes:

• si before e sounds like a soft ś
• j in Polish sounds like English y
• ż sounds like the s in measure
• stress is usually on the second-to-last syllable:
  • teren
  • pasieki
  • jest
  • duży

Yes. Duży is a very common everyday adjective meaning big or large.

In this sentence, both are fine in English:

• The apiary grounds are big.
• The area of the apiary is large.

Polish duży is broad and common, much like English big/large. If you wanted a more formal or literary word, Polish might use something else, but duży is completely normal here.

Its main meaning is apiary, meaning a place where beehives are kept.

So:

• pasieka = apiary
• teren pasieki = the grounds/area of the apiary

It is a fairly specific word connected with beekeeping, not a general word for a farm or field.