Kupię składniki na obiad, chyba że w domu są jeszcze mrożone warzywa.

Kupię means I will buy.

It comes from the verb kupić, which is perfective. In Polish, perfective verbs do not normally have a true present-tense meaning. Their present-looking forms are used to talk about the future.

So:

• kupuję = I am buying / I buy (imperfective, present)
• kupię = I will buy (perfective, future)

In this sentence, kupię składniki suggests a single completed action: I’ll buy the ingredients.

Polish often leaves out subject pronouns when they are clear from the verb ending.

The ending in kupię already tells you the subject is I:

• kupię = I will buy
• kupisz = you will buy
• kupi = he/she/it will buy

So Ja kupię składniki... is possible, but ja is unnecessary unless you want extra emphasis, such as I’ll buy them.

Składniki means ingredients.

Na obiad literally means for dinner / for lunch, depending on how obiad is understood in context.

So składniki na obiad means:

• ingredients for dinner
• ingredients for lunch
• more naturally, ingredients for the meal

A native English speaker should know that obiad is a culturally specific meal word in Polish. It often refers to the main cooked meal of the day, which may be earlier than what English speakers think of as dinner.

The preposition na is very common when talking about something intended for a purpose, event, or meal.

So:

• na obiad = for dinner / for lunch
• na śniadanie = for breakfast
• na kolację = for supper / dinner

Here, na obiad tells us what the ingredients are meant for.

It uses the accusative case, and obiad has the same form in nominative and accusative singular, so you do not see a change in the noun itself.

Chyba że means unless or except if.

It introduces an exception to what was just said:

• Kupię składniki na obiad... = I’ll buy ingredients for dinner...
• ...chyba że w domu są jeszcze mrożone warzywa. = ...unless there are still frozen vegetables at home.

So the idea is:

I’ll buy ingredients for dinner, unless there are still frozen vegetables at home.

This is a very common Polish structure.

Because chyba że introduces a subordinate clause, Polish normally puts a comma before it.

So:

• Kupię składniki na obiad, chyba że...

This is similar to how English often separates unless clauses with a comma when they come after the main clause.

Because the sentence is talking about a present situation, not a future one.

są jeszcze mrożone warzywa means:

• there are still frozen vegetables

The speaker is saying:

I’ll buy ingredients, unless there are still frozen vegetables at home right now.

If you used będą, it would mean will be, which would change the meaning to a future condition.

Here jeszcze means still.

So:

• są jeszcze mrożone warzywa = there are still frozen vegetables

It suggests that maybe some frozen vegetables were already there before, and the speaker is wondering whether they remain.

Depending on context, jeszcze can mean several things, such as:

• still
• yet
• more
• another

But in this sentence, still is the best fit.

W domu means at home or in the house.

The preposition w requires the locative case when it means in a place. The noun dom becomes domu in the locative singular.

So:

• dom = house / home
• w domu = in the house / at home

This is a very common phrase in Polish, and learners should memorize it as a set expression.

Because mrożone warzywa is the subject of the clause after są.

The basic structure is:

• w domu są mrożone warzywa
• at home there are frozen vegetables

Since warzywa is nominative plural here, the adjective must agree with it:

• mrożone = frozen
• warzywa = vegetables

So both words are in the nominative plural.

You would get mrożonych warzyw in other contexts, for example after some negative or quantity expressions, but not here.

Here it is nominative plural, because it is the subject of są.

You are right that the form can look the same as the accusative plural for non-masculine-personal nouns. But syntactically, in this sentence, it is nominative:

• są warzywa = there are vegetables

So even though the form may match accusative in some patterns, its function here is clearly nominative.

Yes, Polish word order is flexible, but the original version sounds natural and neutral:

• Kupię składniki na obiad, chyba że w domu są jeszcze mrożone warzywa.

You could also hear variations such as:

• Kupię składniki na obiad, chyba że są jeszcze w domu mrożone warzywa.
• Chyba że w domu są jeszcze mrożone warzywa, kupię składniki na obiad.

But changing the order can shift emphasis or make the sentence sound less neutral. For a learner, the original sentence is the safest model.

It depends on context and on how you compare Polish meal culture with English-speaking meal culture.

In Polish, obiad usually means the main cooked meal of the day. Depending on the family and schedule, that may correspond more closely to:

• lunch
• dinner
• sometimes just the main meal

So when translating, both lunch and dinner may be possible. The important thing for understanding the Polish is that obiad is a standard everyday meal term, not a special or formal word.