Djeca gledaju labudovo gnijezdo pokraj jezera.

Djeca is the nominative plural form meaning children, and it is the subject of the sentence.

A useful thing to know is that this noun is irregular:

• singular: dijete = child
• plural: djeca = children

So even though English has child / children, Croatian has dijete / djeca.

Because djeca is the subject, it appears in the nominative case.

Gledaju is the 3rd person plural present tense of gledati.

It agrees with the subject djeca:

• ja gledam = I look / I am looking
• ti gledaš = you look
• on/ona/ono gleda = he/she/it looks
• oni/one/ona gledaju = they look

Since djeca means children, the verb must be plural: gledaju.

It can mean all of those, depending on context.

The present tense in Croatian often covers both:

• they look at
• they are looking at
• they watch / are watching

Also, gledati usually suggests actively looking or watching, not just accidentally seeing something. So it is closer to look at or watch than to see.

Croatian often uses a possessive adjective where English uses 's.

So:

• labud = swan
• labudov / labudova / labudovo = swan's

That gives:

• labudovo gnijezdo = the swan's nest / a swan's nest

This is very common with people and animals.

You can also say gnijezdo labuda, which literally means the nest of a swan / the swan, but labudovo gnijezdo is very natural and compact.

Because it has to agree with gnijezdo.

Gnijezdo is:

• neuter
• singular
• here in the accusative (same form as nominative for this noun)

The possessive adjective must match that, so you get:

• masculine: labudov
• feminine: labudova
• neuter: labudovo

Since gnijezdo is neuter, the correct form is labudovo.

Gnijezdo is the direct object of gledaju, so it is in the accusative case.

However, for many neuter singular nouns in Croatian, the nominative and accusative forms are the same.

So:

• nominative: gnijezdo
• accusative: gnijezdo

That is why the form does not visibly change.

Because pokraj normally takes the genitive case.

The base noun is:

• jezero = lake

Its genitive singular is:

• jezera

So:

• pokraj jezera = beside the lake / near the lake

This is a very common pattern in Croatian: certain prepositions require a specific case, and pokraj is one of the prepositions that takes the genitive.

Pokraj means something like:

• beside
• next to
• near

In this sentence, it tells you where the nest is located.

It is similar in meaning to kraj or pored in many contexts, though the exact nuance can vary a little by style or region. For a learner, it is enough to remember:

• pokraj + genitive = beside / near

Because Croatian does not have articles like English a and the.

So a Croatian sentence often leaves definiteness to be understood from context.

That means djeca, labudovo gnijezdo, and jezera can be understood as:

• children / the children
• a swan's nest / the swan's nest
• a lake / the lake

The exact interpretation depends on the situation, not on an article.

Croatian word order is relatively flexible because the case endings show the grammatical relationships.

So this sentence could be rearranged, for example:

• Djeca gledaju labudovo gnijezdo pokraj jezera.
• Djeca pokraj jezera gledaju labudovo gnijezdo.
• Labudovo gnijezdo pokraj jezera gledaju djeca.

These versions do not all sound equally neutral, though.

The original order is a very natural, neutral way to say it:

• subject: Djeca
• verb: gledaju
• object: labudovo gnijezdo
• location phrase: pokraj jezera

Different orders are usually used to shift emphasis or focus.