Learn Hardcore Croatian: Na tavanu naše kuće držimo stare udžbenike gramatike i rječnike. - In the attic of our house we keep old grammar textbooks and dictionaries.

In na tavanu, tavanu is locative singular (masculine noun tavan – “attic”), because the sentence describes a location where something is kept:

Na tavanu držimo… = We keep them in/on the attic (location – no movement).

If you talked about movement to the attic, you would use the accusative:

Idemo na tavan. – We are going to the attic. (movement toward a place)

What case is naše kuće, and why is it used here?

Naše kuće is genitive singular:

naše – possessive adjective “our”, genitive singular feminine
kuće – genitive singular of kuća (“house”)

Genitive is used here to express possession:

na tavanu naše kuće = “in the attic of our house”.

In Croatian, possession is very often expressed by [noun in genitive] after another noun:

tavan naše kuće – the attic of our house
vrata sobe – the door of the room
knjiga prijatelja – a friend’s book / the book of a friend

Why is it naše kuće and not naša kuća?

Because naša kuća would be nominative singular (“our house” as the subject), but here “our house” is not the subject.

We have the phrase:

na tavanu naše kuće – “in the attic of our house”

Here, kuće depends on tavanu: it tells us whose attic. That relationship is expressed with genitive, so:

nominative: naša kuća (Our house is big.) – Naša kuća je velika.
genitive: naše kuće (the attic of our house) – tavan naše kuće

What case are udžbenike and rječnike, and why?

Both udžbenike and rječnike are accusative plural masculine nouns:

udžbenik → udžbenike
rječnik → rječnike

They are in the accusative because they are the direct objects of the verb držimo (“we keep”):

Držimo što? – udžbenike i rječnike.

So the structure is:

(Mi) držimo stare udžbenike gramatike i rječnike.
Subject (implied) + verb + direct object in accusative.

Why is gramatike in that form in udžbenike gramatike?

Gramatike is genitive singular of gramatika (“grammar”).

The structure udžbenike gramatike literally means:

“textbooks of grammar”

Croatian often uses noun + noun in genitive to express “X of Y”:

udžbenici gramatike – textbooks of grammar
udžbenici biologije – textbooks of biology
učenik matematike – a student of mathematics

You could also say gramatičke udžbenike (“grammatical textbooks” / “grammar textbooks”), using an adjective instead of a genitive noun. That shifts the nuance slightly:

udžbenike gramatike – textbooks specifically of the subject “grammar”.
gramatičke udžbenike – more like “grammar-related textbooks” (could be context-dependent).

In practice, udžbenike gramatike is the most natural for school subject textbooks.

What exactly does držimo mean here, and how is it different from imamo or čuvamo?

Držimo is 1st person plural of držati, here meaning “to keep / to store”:

Na tavanu naše kuće držimo… – We keep / store … in the attic.

Nuances:

držati – to keep something somewhere, usually neutral:
- Držimo knjige na polici. – We keep books on the shelf.
imati – “to have”, expresses possession, not where you keep it:
- Imamo stare udžbenike. – We have old textbooks.
čuvati – “to keep / to look after / to preserve”, with a sense of protecting or caring:
- Čuvamo stare udžbenike. – We keep/preserve old textbooks (because they’re important).

In the attic sentence, držimo nicely emphasizes where we keep the books.

Why is the adjective stare used in that form?

Stare is the accusative plural form of the adjective star (“old”) for masculine inanimate nouns.

It agrees with the nouns udžbenike and rječnike in:

gender – masculine (inanimate)
number – plural
case – accusative

So:

nominative plural: stari udžbenici, stari rječnici
accusative plural: stare udžbenike, stare rječnike

In the sentence:

držimo stare udžbenike gramatike i rječnike
– stare modifies both udžbenike and rječnike.

Could the word order be changed, for example: Stare udžbenike gramatike i rječnike držimo na tavanu naše kuće?

Yes. Croatian word order is relatively flexible. Your variant:

Stare udžbenike gramatike i rječnike držimo na tavanu naše kuće.

is grammatically correct and natural. The main differences are in emphasis and information flow:

Original: Na tavanu naše kuće držimo…
- Starts with location, highlighting where.
Variant: Stare udžbenike… držimo na tavanu naše kuće.
- Starts with what we keep, then adds where.

Both are fine; choice depends on what you want to emphasize first.

Why is it na tavanu naše kuće and not u tavanu naše kuće?

In standard usage:

tavan = attic / loft (space at the top of a house)
The natural preposition is na: na tavanu = “in the attic”.

U tavanu is not idiomatic. Speakers would instead say:

u potkrovlju – in the attic/loft space
u kući – in the house
na tavanu – (up) in the attic

So:

Na tavanu naše kuće držimo… – We keep them in the attic of our house.

How do udžbenik and rječnik form their plural and cases?

Both are regular masculine nouns.

udžbenik (textbook):

N sg: udžbenik
G sg: udžbenika
D/L sg: udžbeniku
A sg: udžbenik
I sg: udžbenikom
N pl: udžbenici
G pl: udžbenika
D/L pl: udžbenicima
A pl: udžbenike
I pl: udžbenicima

rječnik (dictionary):

N sg: rječnik
G sg: rječnika
D/L sg: rječniku
A sg: rječnik
I sg: rječnikom
N pl: rječnici
G pl: rječnika
D/L pl: rječnicima
A pl: rječnike
I pl: rječnicima

In the sentence, we use accusative plural: udžbenike, rječnike.

Where does rječnik come from, and how is it related to riječ?

Rječnik is derived from riječ (“word”) + the suffix -nik (often meaning a person or a thing related to something).

There is a small stem change:

riječ → rječ-
- -nik = rječnik

So literally, rječnik is something like a “word-book” – a dictionary.

Other similar formations:

rad (work) → radnik (worker)
škola (school) → školnik (obsolete/rare, but same pattern)
vrt (garden) → vrtlar (gardener – different suffix, same idea)

Could I say u potkrovlju naše kuće instead of na tavanu naše kuće?

Yes, but there is a small nuance:

na tavanu naše kuće – “in the attic of our house”, slightly more colloquial, focusing on the space as a part of the house where you store things.
u potkrovlju naše kuće – “in the loft / in the attic space of our house”, sometimes sounds a bit more architectural or neutral.

Both are correct; na tavanu is extremely common in everyday speech for “in the attic”.