Ispod prozora je stajao stari traktor koji još uvijek radi.

Because ispod normally takes the genitive case, so prozor changes to prozora.

• prozor = window
• ispod prozora = below/under the window

This is one of the common things learners notice in Croatian: prepositions often require a specific case.

Ispod means below, under, or beneath.

In this sentence, Ispod prozora gives the location of the tractor:

• Ispod prozora = under/below the window

It is a very common preposition for physical position.

Croatian word order is much more flexible than English word order. Starting with Ispod prozora puts the location first, as the setting of the sentence:

• Ispod prozora je stajao stari traktor...

This is natural in Croatian and can sound more descriptive or narrative. English usually prefers A/the old tractor was standing below the window, but Croatian can move parts around more freely without changing the basic meaning.

Je stajao is the normal past tense form in Croatian.

Croatian past tense is usually made with:

• a form of biti (sam, si, je, smo, ste, su)
• plus the -ao / -la / -lo participle form

So:

• je stajao = he/it was standing / stood

Here traktor is masculine singular, so the participle is stajao.

In everyday language, the auxiliary je can sometimes be omitted in certain styles, but the standard full form here is je stajao.

Because je is a clitic in Croatian. Clitics usually go in the second position of the clause, not necessarily directly after the subject.

So in:

• Ispod prozora je stajao stari traktor

the first unit is Ispod prozora, and then the clitic je comes next.

This is very normal Croatian word order.

Literally, yes: stajao comes from stajati, which means to stand.

But with objects like vehicles or buildings, it often means something more like:

• was standing
• was parked
• was situated
• was there

So for a tractor, stajao does not mean it had legs and was standing upright. It means it was positioned there, probably motionless.

In Croatian, adjectives usually come before the noun:

• stari traktor = old tractor

That is the normal order. Putting the adjective after the noun is unusual in ordinary neutral sentences and is only used in special stylistic or poetic cases.

Because Croatian has no articles like English a/an/the.

So:

• stari traktor can mean an old tractor or the old tractor

Which one is meant depends on the context. In this sentence, the meaning is understood from the situation, not from an article.

Koji is a relative pronoun here, meaning that, which, or who depending on context.

It connects traktor with the extra information:

• stari traktor koji još uvijek radi
• the old tractor that still works

So koji introduces the relative clause and refers back to traktor.

Because koji must match the noun it refers to, and here it refers to traktor, which is:

• masculine
• singular
• the subject of radi

So the nominative masculine singular form is koji.

Compare:

• traktor koji radi = tractor that works
• kuća koja stoji tamo = house that stands there
• pismo koje sam dobio = letter that I received

Because the relative clause describes something that is still true now.

• je stajao = was standing / stood
• još uvijek radi = still works / is still working

So the sentence means that in the past there was an old tractor under the window, and that tractor still functions now.

If the speaker wanted to say it worked at that past time, but not necessarily now, they might use a past form instead.

Još uvijek means still.

You will also hear just još in some contexts, but još uvijek clearly emphasizes continuation:

• još uvijek radi = it still works

It is a very common expression in Croatian.

Roughly:

• još can mean still, more, or yet, depending on context
• još uvijek specifically means still, in the sense of continuing up to now

Because this is a restrictive relative clause: it identifies which tractor is being talked about.

• stari traktor koji još uvijek radi = the old tractor that still works

In Croatian, restrictive relative clauses are usually written without a comma.

A comma would be more likely if the clause were additional, non-essential information.

It is also very commonly used for machines.

With machines, raditi means:

• to work
• to function
• to run

So:

• Traktor radi = The tractor works / is running
• Auto ne radi = The car is not working
• Sat još radi = The clock still works

This is completely normal Croatian usage.

A simple learner-friendly approximation is:

• još ≈ yosh
• uvijek ≈ oo-vyeke or oo-vyek

A few useful notes:

• j in Croatian sounds like English y in yes
• š sounds like sh
• ij/je combinations can be tricky, and actual pronunciation varies a little by region and speech speed

So još uvijek radi sounds roughly like:

• yosh oo-vyek rah-dee

Not with exactly the same meaning.

• ispod prozora = below/under the window
• pod prozorom = under the window

These can overlap, but they are not always identical. Ispod often highlights position lower than something, while pod is the usual simple under. In many everyday situations both might be understandable, but the sentence as given uses ispod prozora, which is perfectly natural.