Szkła progresywne są drogie.

Here szkła means lenses in the optician’s sense. The basic noun szkło literally means glass, but in context it can also mean a lens or a glass lens.

So szkła progresywne refers to progressive lenses, not necessarily the whole pair of glasses.

In this sentence, szkła is plural.

• singular: szkło
• plural: szkła

A confusing point is that szkła can also be the genitive singular form of szkło, but here the verb są means are, so we know szkła must be plural: Progressive lenses are expensive.

In Polish, adjectives often come before the noun, but some adjectives—especially ones that classify a thing by type—very often come after the noun.

So szkła progresywne sounds like a standard product/category name: progressive lenses.

You may also hear progresywne szkła, but szkła progresywne is very natural when talking about a specific kind of lens in an optical/technical context.

It is in the nominative plural.

Why?

Because it is the subject of the sentence:

• Szkła progresywne = the thing being talked about
• są drogie = are expensive

So the structure is:

• subject: szkła progresywne
• verb: są
• predicate adjective: drogie

Because Polish adjectives must agree with the noun in number, gender, and case.

Here:

• szkła is plural
• it refers to things, not people
• so Polish uses the non-masculine-personal plural adjective form

That is why the adjective is progresywne.

A very important Polish pattern is:

• masculine personal plural: -i / -y type forms
• non-masculine-personal plural: often -e

Since lenses are objects, not a group of men or people, progresywne is the correct form.

Są is the 3rd person plural present tense of być (to be), so it means are.

• jest = is
• są = are

In this sentence:

• Szkła progresywne są drogie = Progressive lenses are expensive.

Unlike in some other languages, in normal standard Polish you usually do not omit są in this kind of sentence.

For the same reason as progresywne: it must agree with szkła.

Since szkła is:

• plural
• non-masculine-personal
• nominative

the adjective must also be in that form:

• drogie

Why not drogi?

• drogi is not the right plural form for this noun.

Why not drogimi?

• drogimi is instrumental plural, and that is not what we need here.

After być with an adjective, Polish normally uses the nominative:

• Szkła są drogie
• Okulary są nowe
• Dom jest duży

It can mean both, and context tells you which meaning is intended.

With things:

• To jest drogie = This is expensive.

With people:

• mój drogi przyjaciel = my dear friend

In Szkła progresywne są drogie, the meaning is clearly expensive because we are talking about lenses.

Yes, that is grammatically correct.

Both are possible:

• Szkła progresywne są drogie
• Progresywne szkła są drogie

The version with szkła progresywne sounds a bit more like a named category or technical term. The version with progresywne szkła sounds a bit more like ordinary descriptive word order.

In real usage, both can occur.

Not exactly.

• szkła progresywne = progressive lenses
• okulary progresywne = progressive glasses / glasses with progressive lenses

So szkła refers to the lenses themselves, while okulary refers to the whole pair of glasses.

Because Polish does not have articles like English a/an/the.

So Szkła progresywne są drogie can mean:

• Progressive lenses are expensive
• The progressive lenses are expensive

Context tells you which meaning is intended.

It is pronounced roughly like shkwa.

A few helpful points:

• sz sounds like English sh
• kł is pronounced with ł = w
• so szkła comes out approximately as SHKWA

That consonant cluster can feel awkward at first, but it is normal in Polish.