Czytelnik odszedł z czytelni.

Because after z meaning from / out of, Polish uses the genitive case.

The base form is czytelnia = reading room.
Its genitive singular form is czytelni.

So:

• czytelnia = nominative, dictionary form
• z czytelni = from the reading room

This is very common in Polish:

• z domu = from the house
• z pracy = from work
• z biblioteki = from the library

No. z can take different cases depending on the meaning.

Most importantly:

• z + genitive = from / out of
• z + instrumental = with

So in this sentence:

• z czytelni = from the reading room → genitive

Compare:

• z kolegą = with a friend → instrumental

This is a very common thing learners ask about, because English uses the same word with/from very differently, while Polish changes the case.

Not exactly.

• biblioteka = library
• czytelnia = reading room

A czytelnia is usually a place where people sit and read, often inside a library, school, archive, or similar institution.

So Czytelnik odszedł z czytelni specifically means the person left the reading room, not necessarily the whole library building.

Yes. Both come from the verb czytać = to read.

• czytelnik = reader
• czytelnia = reading room

The endings help show the type of word:

• -nik often forms a noun for a person
• -nia often forms a noun for a place

So these words are related in meaning:

• czytać = to read
• czytelnik = reader
• czytelnia = reading room

That makes the sentence easy to recognize as being about reading / a reading place.

Odszedł is the past tense, masculine singular form of odejść.

So it tells you that:

• the action happened in the past
• the subject is one person
• that person is grammatically masculine

Compare:

• odszedł = he left
• odeszła = she left
• odeszło = it left
• odeszli = they left (mixed group or all male people)
• odeszły = they left (all-female group or non-masculine group)

In Polish past tense, the verb agrees with the subject in gender and number, which is something English does not usually do.

These verbs are similar, but not identical.

• odejść / odszedł = go away, leave
• wyjść / wyszedł = go out, exit
• pójść / poszedł = go

In this sentence, odszedł z czytelni focuses on the idea that the reader left / went away from the reading room.

If you said wyszedł z czytelni, that would emphasize physically going out of the room.
If you said poszedł, you would usually need more context about where he went.

So odszedł is natural here, with a sense like left or went away from.

Odejść is perfective. Its imperfective partner is odchodzić.

That matters because perfective verbs usually describe a completed whole action.

So:

• odszedł = he left / he went away as a completed event
• odchodził = he was leaving / used to leave / kept leaving, depending on context

In this sentence, the action is a single completed event, so odszedł is the natural choice.

Grammatically, czytelnik is a masculine noun. In a sentence like this, together with odszedł, it clearly refers to a masculine singular subject.

The specifically feminine form is:

• czytelniczka = female reader

So:

• Czytelnik odszedł z czytelni. = a male reader left the reading room
• Czytelniczka odeszła z czytelni. = a female reader left the reading room

In some contexts, masculine forms can be used more generically, but this sentence is grammatically masculine.

Yes, absolutely.

Polish often omits subject pronouns and even explicit subjects when the verb already makes the meaning clear enough.

• Odszedł z czytelni. = He left the reading room.

Because odszedł is masculine singular past tense, Polish speakers already know the subject is he / a masculine singular person.

Adding Czytelnik makes the subject explicit. That can help with clarity, contrast, or style.

No. Polish word order is fairly flexible.

Czytelnik odszedł z czytelni is a neutral, straightforward order:

• subject
• verb
• prepositional phrase

But other orders are possible, for example:

• Z czytelni odszedł czytelnik.
• Odszedł z czytelni czytelnik.

These can sound more marked and may change what is emphasized. English word order is much stricter, but Polish often uses word order for focus and emphasis, not just grammar.

The ł in modern Polish is pronounced like an English w sound.

So odszedł sounds approximately like ot-SHEDw.

A few helpful points:

• sz sounds like English sh
• ł sounds like w
• the final consonants may sound slightly devoiced in natural speech

So even though the spelling looks intimidating, the pronunciation is quite regular once you know the letter combinations.

Yes. On its own, odejść / odszedł can sometimes be used euphemistically to mean passed away.

But context makes the meaning clear.

Here, because we have z czytelni = from the reading room, the meaning is simply left / went away from the reading room. There is no ambiguity in this sentence.