Learn Hardcore Croatian: U stvarnosti znanstvenik samo gleda kroz teleskop na krovu zgrade. - In reality the scientist male just looks through a telescope on the roof of the building.

Croatian has no articles (a / an / the) at all, so znanstvenik simply means scientist / the scientist / a scientist, depending on context.

The definiteness (whether it’s a or the) is understood from the situation, not from a separate word. Here, from context, we understand it as the scientist, but the form znanstvenik itself doesn’t change.

Why does Croatian use gleda for is looking? I don’t see a separate word like is.

Croatian usually expresses both:

English looks (habitual) and
English is looking (right now)

with the same present tense form: gleda.

Context tells you whether it’s:

znanstvenik gleda = the scientist looks / watches (in general)
znanstvenik (sada) gleda = the scientist is (now) looking

There is no auxiliary to be in the present tense here, and no -ing form; the simple present gleda covers both meanings.

What does samo do here, and why is it before gleda?

samo means only / just.

Its position determines what is being restricted:

znanstvenik samo gleda
→ the scientist only looks / is just looking (he doesn’t do anything else)
samo znanstvenik gleda
→ only the scientist is looking (no one else is looking)

So in the given sentence, samo is placed before the verb gleda to say that looking is the only action he is doing.

Why is it kroz teleskop and not something like preko teleskopa?

Different prepositions express different spatial ideas:

kroz
- accusative = through (passing from one side to the other, or seeing through something)
  → kroz teleskop = through the telescope
preko
- genitive = over / across / via
  → preko mosta = over the bridge
  → preko interneta = via the Internet

When talking about looking through an optical instrument, the natural preposition is kroz, so kroz teleskop is the standard way to say through a telescope.

Why is teleskop in that form? What case is it, and why?

After kroz, Croatian always uses the accusative case.

Nominative (dictionary form): teleskop
Accusative singular (for an inanimate masculine noun): also teleskop

So kroz teleskop is kroz + accusative, meaning through the telescope.

You do not see a change in form here because for many inanimate masculine nouns, nominative and accusative singular look the same.

Why is it na krovu zgrade and not na krov zgrade? What’s the difference?

The preposition na can take:

accusative → direction, movement onto something
locative → place, position on something (no movement)

Here we have:

na krovu = on the roof
- krov → krovu is locative singular (where? on the roof)

If you said:

na krov (accusative), that would mean onto the roof and would imply movement:
- penje se na krov = he is climbing onto the roof

Since in the sentence the telescope (or the scientist) is already located on the roof, we use na krovu, not na krov.

What case is zgrade, and what does it express?

zgrade here is genitive singular of zgrada (building).

Nominative: zgrada (a building)
Genitive: zgrade (of a building / of the building)

The phrase krov zgrade = the roof of the building.

So na krovu zgrade literally means on the roof of the building:

na → preposition
krovu → locative (on the roof)
zgrade → genitive (of the building)

Does na krovu zgrade describe the telescope or the scientist? Who is on the roof?

Literally, word-for-word, the phrase can be read as:

gleda kroz teleskop [koji je] na krovu zgrade
→ he is looking through a telescope [which is] on the roof of the building

So the default interpretation is that the telescope is on the roof.

In normal speech, though, people would usually understand that the scientist and his telescope are both on the roof, because that is how telescopes are used. Grammatically, it attaches most naturally to teleskop, but context determines the actual scene.

If you wanted to make it crystal clear that the scientist is on the roof, you could say, for example:

Znanstvenik je na krovu zgrade i gleda kroz teleskop.
→ The scientist is on the roof of the building and is looking through a telescope.

What is the difference between gledati and pogledati? Could I say samo pogleda kroz teleskop?

Croatian verbs come in aspect pairs:

gledati = imperfective (ongoing, repeated, or uncompleted action)
→ gleda = is looking / looks
pogledati = perfective (a single complete act of looking, “to have a look”)
→ pogleda = looks (once) / takes a look

In your sentence, we are talking about what he is doing (as an activity), so gledati (imperfective) is the natural choice.

If you said:

znanstvenik samo pogleda kroz teleskop

that would suggest he just gives it a quick look once (a single completed glance), which is a different nuance from he is just looking / just observing through the telescope.

What exactly does u stvarnosti mean, and is it the same as stvarno or u realnosti?

u stvarnosti literally means in reality and functions as an adverbial phrase, like English in reality / actually.

u stvarnosti = in reality, often contrasting real life with expectations, imagination, theory, etc.
stvarno = really / truly / actually, more like an adverb modifying a verb or adjective:
- stvarno je dobar = he’s really good
u realnosti exists, but u stvarnosti is much more common and idiomatic in this sense.

So starting the sentence with U stvarnosti nicely sets up a contrast with some previous idea (for example, what we imagined the scientist was doing).

Should there be a comma after U stvarnosti?

Both are possible:

U stvarnosti, znanstvenik samo gleda…
U stvarnosti znanstvenik samo gleda…

In short, with short initial adverbials like u stvarnosti, Croatian often omits the comma, especially in modern, less formal writing.

Adding the comma is not wrong; it just slightly emphasizes the pause and the contrast (In reality, ...). Many native speakers would write it without a comma in everyday text.

How would I say female scientist here? Does znanstvenik imply male?

Yes, znanstvenik is the masculine form: scientist (male).

The feminine form is:

znanstvenica = female scientist

So, for a female scientist, you would say:

U stvarnosti znanstvenica samo gleda kroz teleskop na krovu zgrade.