To filia, czyli część biblioteki.

Here to works like this is or that is.

So:

• To filia = This is a branch
• To jest filia = also possible, but jest is often omitted in this kind of definition or identification sentence

In Polish, to is very commonly used when you are naming or identifying something.

Both are correct.

• To filia sounds natural and concise.
• To jest filia is a little more explicit, like This is a branch.

Polish often leaves out jest in simple identification sentences, especially in definitions, labels, or explanations.

Filia means a branch, especially of an institution.

In this sentence, it refers to a branch library or a branch of a library system.

You can also use filia for other organizations, for example:

• filia banku = a bank branch
• filia szkoły = a branch/campus of a school

It is a feminine noun.

Czyli means something like:

• that is
• in other words
• that is to say
• namely

It introduces a clarification or a simpler restatement.

So:

• To filia, czyli część biblioteki. means:
• This is a branch, in other words, part of the library.

A very similar expression is to znaczy, but czyli is often a bit smoother and very common in everyday Polish.

Because część requires the following noun to be in the genitive case.

So:

• część
  • biblioteki = part of the library

This is a very common pattern in Polish:

• część domu = part of the house
• część miasta = part of the city
• część książki = part of the book

So biblioteki is not random here; it is the grammatically required form after część.

It is genitive singular.

The base form is:

• biblioteka = library

After część, it changes to:

• biblioteki = of the library

This is because część usually takes the genitive.

Filia is in the nominative singular.

That is the dictionary form of the noun, and it is used here because the sentence is identifying what something is:

• To filia. = This is a branch.

Since filia is a feminine noun, its nominative singular form ends in -a.

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

So filia can mean:

• a branch
• the branch

The exact meaning depends on context.

Likewise, biblioteki can mean:

• of a library
• of the library

In this sentence, context makes it clear that part of the library is meant.

Not completely. Polish word order is fairly flexible, although some versions sound more natural than others.

The given sentence:

• To filia, czyli część biblioteki.

is natural and clear.

You could also see:

• To część biblioteki, czyli filia.

but that changes the emphasis slightly.

In the original sentence, the speaker first names the thing as filia, and then explains it with czyli część biblioteki.

Approximate pronunciation:

• filia ≈ FEE-lya
• czyli ≈ CHIH-li or CHY-li
• część is harder for English speakers; it sounds roughly like chenshch, with a nasal vowel

A few helpful notes:

• cz sounds like English ch
• li before a vowel often sounds soft, like ly
• ę is a nasal vowel
• ść is a very soft consonant cluster

If pronunciation feels difficult, that is normal—especially with część.

Usually no, not in the most direct sense.

Filia specifically means a branch of a larger institution, usually in another location or as a subordinate unit.

If you mean a section inside one building or inside one organization, Polish might use other words, such as:

• dział = department/section
• oddział = department/branch/ward, depending on context
• sekcja = section

So for a library branch, filia is a very natural word.

Yes, it is natural, especially in an explanatory or educational context.

It sounds like a simple definition:

• To filia, czyli część biblioteki.

If you wanted to sound a bit fuller in conversation, you might say:

• To jest filia, czyli część biblioteki.

But the shorter version is completely normal.