Podszewka jest czysta.

Because czysta has to agree with podszewka in gender, number, and case.

• podszewka is feminine singular
• the sentence is in the nominative
• so the adjective also takes the feminine singular nominative form: czysta

Compare:

• czysty = masculine
• czysta = feminine
• czyste = neuter

So Podszewka jest czysta is grammatically matched.

A very common clue in Polish is the ending -a. Most nouns ending in -a are feminine, and podszewka is one of them.

Because it is feminine, any adjective describing it must also be feminine:

• czysta podszewka
• Podszewka jest czysta

As always, there are some exceptions in Polish, but in this case the -a ending really does signal a feminine noun.

Jest is the 3rd person singular present tense of być, meaning to be.

So here it means is:

• podszewka = the lining
• jest = is
• czysta = clean

Unlike in some other Slavic languages, Polish normally does use jest in this kind of present-tense sentence. So Podszewka jest czysta is the normal full sentence.

Usually, no, not in normal standard Polish.

Podszewka jest czysta is the standard form.
If you say Podszewka czysta, it can sound:

• telegraphic
• poetic
• like a label, note, or very clipped speech

So for a learner, it is safest to keep jest here.

Both are in the nominative singular here.

• podszewka is the subject, so nominative makes sense
• czysta is a predicate adjective after jest, and predicate adjectives in Polish normally stay in the nominative and agree with the subject

So:

• podszewka = nominative singular feminine
• czysta = nominative singular feminine

This is worth noticing because noun complements after być often behave differently, for example with the instrumental:

• Ona jest nauczycielką = She is a teacher

But adjectives like czysta stay nominative:

• Ona jest czysta
• Podszewka jest czysta

In this sentence, czysta is not directly attached to the noun as part of a noun phrase. It is a predicate adjective, so it comes with jest:

• Podszewka jest czysta = The lining is clean

If you put the adjective directly before the noun, you get a different structure:

• czysta podszewka = a clean lining / clean lining

So:

• czysta podszewka = adjective + noun
• podszewka jest czysta = subject + is
  • adjective

Both are correct, but they are used in different sentence patterns.

Yes, Polish word order is more flexible than English, although the neutral order here is:

• Podszewka jest czysta.

Other orders are possible, but they change the emphasis:

• Czysta jest podszewka.
  This puts more focus on clean
• Jest czysta.
  This is possible if the subject is already understood from context

For most learners, the basic order Podszewka jest czysta is the best default.

A learner-friendly approximation is:

pod-SHEF-ka

A few useful pronunciation points:

• sz sounds like English sh
• w normally sounds like English v
• but before the voiceless k, that w is pronounced more like f

So the middle of the word sounds like -szef-, not like English w.

No. Polish has no articles like English the or a/an.

So Podszewka jest czysta can mean:

• The lining is clean
• A lining is clean

In real use, context tells you which meaning is intended. If you want to make it more specific, you can add a word like:

• Ta podszewka jest czysta. = This/The lining is clean.

Yes. It is a very normal structure:

• noun + jest + adjective

You can use the same pattern with many other adjectives:

• Koszula jest czysta. = The shirt is clean.
• Sukienka jest nowa. = The dress is new.
• Podszewka jest brudna. = The lining is dirty.

So this sentence is a good model for making many simple descriptive statements in Polish.