Learn Hardcore Polish: Biblioteka jest cicha, dlatego uczę się tam szczególnie wieczorem. - The library is quiet, therefore I study there especially in the evening.

In Polish, adjectives agree with the noun they describe in gender, number, and case. Biblioteka is a feminine noun in the nominative singular, so you need the feminine adjective form cicha (“quiet”). Cicho is an adverb (“quietly”), which would describe a verb, not the library.

What exactly is dlatego and how does it function in the sentence?

Dlatego is a conjunctive adverb meaning “therefore” or “that’s why.” It links the first clause (“The library is quiet”) to the second (“I study there…”), showing cause and effect. It always needs a comma before it when it connects two independent clauses.

Could we replace dlatego with więc or zatem, and are there any differences?

Yes. You can say więc (“so/then”) or zatem (“thus”) in place of dlatego with almost the same meaning.

więc is more conversational:
Biblioteka jest cicha, więc uczę się tam wieczorem.
zatem is slightly more formal:
Biblioteka jest cicha, zatem uczę się tam wieczorem.
In each case, you still use a comma before the word.

Why does the verb uczę się immediately follow dlatego?

When you start a clause with an adverb or conjunctive adverb like dlatego, Polish word order places the verb right after it. This is typical V-X-S (verb-rest-subject) inversion for emphasis or linkers. Here “dlatego uczę się” keeps the flow natural.

What does tam refer to, and is it necessary? Could we say w niej instead?

Tam means “there” and points back to biblioteka. It’s not strictly required—Polish often drops repeated location—but it adds clarity. You could use w niej (“in it”) for a bit more formality:
Biblioteka jest cicha, dlatego uczę się w niej wieczorem.

What is the function of szczególnie in this sentence? Can its position change?

Szczególnie means “especially” or “particularly.” Here it modifies wieczorem, highlighting that evenings are the prime study time. You can move it for emphasis:

Uczę się tam szczególnie wieczorem. (default)
Szczególnie wieczorem uczę się tam. (evening focus)
Uczę się tam wieczorem szczególnie. (less common, more poetic)

Why is wieczorem used to say “in the evening”? Why not another case or form?

Many Polish time expressions use the instrumental singular form of the noun: wieczór → wieczorem. It functions adverbially to mean “during the evening” or “in the evening.” You don’t use the locative here; the instrumental is the standard way.

How do you pronounce biblioteka, and where is the stress?

Biblioteka is pronounced [bee-blyo-TEH-ka]. Polish stress is almost always on the penultimate syllable, so you stress TE in biblioteka.