Ta soczewka jest czysta.

Because soczewka is a feminine singular noun.

In Polish, demonstratives like this/that change to match the noun’s gender:

• ten for masculine singular
• ta for feminine singular
• to for neuter singular

So:

• ta soczewka = this/that lens

Since soczewka ends in -a and is feminine, ta is the correct form.

Because adjectives in Polish must agree with the noun they describe.

Since soczewka is:

• feminine
• singular
• nominative

the adjective must also be:

• feminine
• singular
• nominative

That gives:

• masculine: czysty
• feminine: czysta
• neuter: czyste

So Ta soczewka jest czysta is grammatically matched all the way through.

A very common clue is the ending -a.

Many Polish nouns ending in -a are feminine, especially ordinary everyday nouns like:

• książka = book
• szkoła = school
• soczewka = lens

There are some exceptions in Polish, but for a noun like soczewka, feminine is exactly what you should expect.

The noun phrase ta soczewka is in the nominative singular, because it is the subject of the sentence.

The adjective czysta is also nominative singular feminine, agreeing with soczewka.

So the sentence is built like this:

• ta — nominative singular feminine
• soczewka — nominative singular feminine
• jest — is
• czysta — nominative singular feminine

In normal full sentences like this, jest is standard and natural.

• Ta soczewka jest czysta. = This lens is clean.

You may sometimes hear shorter, more elliptical forms such as:

• Soczewka czysta

but that sounds more like a label, note, checklist item, or very compressed speech. In ordinary complete spoken or written Polish, jest is what you would usually use here.

Yes.

• Ta soczewka jest czysta = This/that lens is clean
• Soczewka jest czysta = The lens is clean / A lens is clean, depending on context

Adding ta points to a specific lens more clearly, like this one. Without it, the sentence is still perfectly correct.

Because Polish normally does not use articles.

English says:

• the lens
• a lens

Polish usually just says:

• soczewka

Context tells you whether it means the lens, a lens, or sometimes this lens if the situation already makes that clear.

That is one of the biggest differences between Polish and English.

Not completely. Polish word order is more flexible than English.

The most neutral version is:

• Ta soczewka jest czysta.

But you could also hear:

• Soczewka jest czysta.
• Czysta jest ta soczewka.

These versions shift emphasis rather than basic meaning.

For a learner, the safest neutral pattern is:

• [demonstrative] + [noun] + jest + [adjective]

So Ta soczewka jest czysta is a very good standard model.

It can often mean either, depending on context.

In everyday Polish, ten / ta / to often covers both this and that when the object is identifiable from the situation.

If you want to be more clearly contrastive, Polish can use:

• ta = this/that
• tamta = that one over there

So:

• ta soczewka = this lens / that lens
• tamta soczewka = that lens over there

A rough English-friendly guide is:

• ta = tah
• soczewka = roughly so-CHEF-ka
• jest = yest
• czysta = roughly CHIS-ta

A few useful sound notes:

• cz sounds like a hard ch sound
• j sounds like English y
• w sounds like English v, but in soczewka it is devoiced before k, so it sounds more like f
• y in czysta is not exactly English i, but CHIS-ta is a decent first approximation

Stress is usually on the second-to-last syllable:

• soCZEWka
• CZYSta

Usually it means a lens, and the exact type depends on context.

It can refer to things like:

• a camera lens
• a contact lens
• a lens in glasses
• a scientific/optical lens

If the context is about eyesight, soczewka can definitely mean contact lens or eyeglass lens. If needed, Polish can be more specific, for example:

• soczewka kontaktowa = contact lens

Yes, but that is not the same sentence type.

• Ta soczewka jest czysta. = This lens is clean.
• Ta czysta soczewka = this clean lens

The first is a full sentence with is. The second is just a noun phrase.

So if you want to describe the lens in a complete statement, use:

• Ta soczewka jest czysta.

If you want a phrase inside a bigger sentence, you can use:

• ta czysta soczewka

In this sentence, czysta is the normal word for clean.

For a lens, English sometimes uses clean and clear in overlapping ways, but Polish usually keeps them more separate:

• czysty / czysta = clean
• przejrzysty / przezroczysty = clear / transparent, depending on context

So if you mean the lens is not dirty, czysta is the right choice.