Wszystkie książki są na półce.

Because książki (books) are not masculine-personal.

In Polish plural, words like all change depending on what kind of noun they describe:

• wszyscy = for masculine-personal groups, usually groups of men or mixed people
  
  • e.g. wszyscy studenci = all the students
• wszystkie = for non-masculine-personal nouns
  
  • e.g. wszystkie książki = all the books

Since books are things, not people, Polish uses wszystkie.

Here książki is the nominative plural form of książka (book).

• singular: książka
• plural: książki

It is nominative because książki is the subject of the sentence:

• Wszystkie książki = all the books
• są = are

So the structure is basically:

• [subject] + [verb] + [location]

Są is the 3rd person plural form of być (to be) in the present tense.

So:

• jest = is (singular)
• są = are (plural)

Because książki is plural, you need są:

• Książka jest na półce. = The book is on the shelf.
• Książki są na półce. = The books are on the shelf.

Because after na meaning on, when you are talking about location (where something is), Polish usually uses the locative case.

So:

• dictionary form: półka = shelf
• locative singular: na półce = on the shelf

This is a very common pattern:

• na stole = on the table
• na krześle = on the chair
• na półce = on the shelf

So in this sentence, na półce means a static location: the books are already there.

Then Polish would usually use the accusative, because that shows movement toward a place.

Compare:

• na półce = on the shelf / located on the shelf
• na półkę = onto the shelf / to the shelf

Examples:

• Książki są na półce. = The books are on the shelf.
• Kładę książki na półkę. = I am putting the books onto the shelf.

This location-vs-movement contrast is very important in Polish.

Yes. In this sentence, wszystkie behaves like an adjective/determiner modifying książki.

It agrees with książki in:

• number: plural
• gender category: non-masculine-personal
• case: nominative

That is why the form is wszystkie.

Polish modifiers have to agree with the noun they describe, much more than in English.

No. Polish does not have articles like a or the.

So książki can mean:

• books
• the books

The exact meaning depends on context.

That is why Wszystkie książki są na półce can naturally mean All the books are on the shelf without any separate word for the.

Yes. Polish word order is more flexible than English because cases show grammatical roles.

The neutral order here is:

• Wszystkie książki są na półce.

But you can also say:

• Na półce są wszystkie książki.

This version puts more focus on na półce or sounds like you are answering Where are all the books?

So the word order can change, but the emphasis changes too.

In this sentence, wszystkie książki means all the books as a group.

If you want to say every book in a more distributive, one-by-one sense, Polish often uses:

• każda książka = every book

Compare:

• Wszystkie książki są na półce. = All the books are on the shelf.
• Każda książka jest na półce. = Every book is on the shelf.

In many contexts the meaning is similar, but the grammar is different:

• wszystkie książki = plural
• każda książka = singular

The singular version would be:

• Wszystka książka? — No, that is not normal here.
• The natural sentence is: Książka jest na półce. = The book is on the shelf.

If you want the whole book, then wszystka książka is also not the usual way. Polish more naturally says:

• cała książka = the whole book

So wszystkie works very naturally in plural with books, but singular usually uses other expressions depending on meaning.

A rough pronunciation is:

• fshist-kye

More carefully:

• wsz sounds roughly like fsh
• y is a Polish vowel that does not exist exactly in English
• tkie sounds roughly like tkye

So the whole word is approximately:

• FSHIS-tkye

This is only an approximation, but it helps.

Because nouns change endings in different cases, and półka is a feminine noun.

In the locative singular, many feminine nouns ending in -ka change to -ce after certain consonants:

• półka → na półce

This kind of spelling/pronunciation change is very common in Polish declension.

So you should learn nouns together with some common case forms, not only the dictionary form.

No, in normal present-tense Polish you should keep są here.

So you say:

• Wszystkie książki są na półce.

not:

• Wszystkie książki na półce. (incomplete as a normal full sentence)

In headlines, notes, or very informal contexts, words may sometimes be omitted, but in standard grammar the verb to be is required here.

Its basic meaning is shelf.

Depending on context, English might translate it as:

• shelf
• sometimes part of a bookcase or cabinet shelf

But in this sentence, the natural meaning is simply:

• on the shelf

So Wszystkie książki są na półce most naturally means that all the books are sitting on a shelf.