U bilježnici je pravokutnik ispao širi od kvadrata, pa je učiteljica nacrtala novu crtu pokraj njega.

U bilježnici means in the notebook in the sense of location, so u takes the locative here.

• bilježnica = notebook
• u bilježnici = in the notebook

Compare:

• u bilježnici = in the notebook, inside it / on its pages → locative
• u bilježnicu = into the notebook → accusative, movement toward it

So this sentence is talking about where the drawing is, not motion into the notebook.

Croatian word order is fairly flexible. The sentence could be rearranged in several ways, but the version here sounds natural and puts the setting first:

• U bilježnici = in the notebook
• je = auxiliary
• pravokutnik = the rectangle
• ispao širi od kvadrata = turned out wider than the square

A key point is that short unstressed words like je often come in second position in the clause. So after the first phrase U bilježnici, the auxiliary je appears.

This is a normal Croatian pattern, not something that maps neatly onto English word order.

Here ispao does not mean literally fell out. In this sentence, ispasti means something like:

• turn out
• come out
• end up

So pravokutnik je ispao širi od kvadrata means the rectangle came out wider than the square or turned out wider than the square.

This is a very common figurative use of ispasti in Croatian.

Because ispao agrees with the subject pravokutnik, which is:

• masculine
• singular
• nominative

In the Croatian past tense, the l-participle agrees with the subject in gender and number.

So:

• pravokutnik je ispao = the rectangle turned out...
• crta je ispala = the line turned out...
• more je ispalo = the sea / it turned out... (neuter)

Yes. Širi is the comparative form of širok = wide.

• širok = wide
• širi = wider

So:

• pravokutnik je širi = the rectangle is wider

In this sentence:

• ispao širi od kvadrata = turned out wider than the square

Croatian comparatives are often irregular enough that it is best to learn them individually.

After a comparative like širi = wider, Croatian often uses od + genitive to mean than.

So:

• širi od kvadrata = wider than the square

Here kvadrata is genitive singular of kvadrat.

Pattern:

• veći od... = bigger than...
• manji od... = smaller than...
• širi od... = wider than...

You may also see nego used in comparisons, but od + genitive is very common.

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

So:

• pravokutnik can mean a rectangle or the rectangle
• kvadrat can mean a square or the square

The exact meaning depends on context. In this sentence, English would naturally use the rectangle and the square, but Croatian does not need articles to express that.

Pa here means something like:

• so
• and so
• then

It connects the two parts of the sentence:

1. the rectangle came out wider than the square
2. as a result, the teacher drew a new line next to it

So pa gives a natural sense of consequence or continuation.

The past tense in Croatian is formed with:

• the auxiliary biti in the present tense
• plus the l-participle

Here:

• je nacrtala = drew / has drawn

And nacrtala agrees with učiteljica, which is feminine singular.

So:

• učiteljica je nacrtala = the female teacher drew

If the subject were masculine:

• učitelj je nacrtao = the male teacher drew

Because crtu is the accusative singular form of crta, and it is the direct object of nacrtala.

• crta = line
• nova crta = a new line
• nacrtala novu crtu = drew a new line

Since crta is feminine singular, the adjective must match it:

• nominative: nova crta
• accusative: novu crtu

Here crta means line, especially a drawn line or stroke.

So nacrtala novu crtu means the teacher drew a new line.

In other contexts, crta can also mean things like a stripe, a mark, or even a character trait, but here the drawing meaning is the relevant one.

Pokraj means beside / next to, and it takes the genitive.

So:

• pokraj njega = next to it / next to him

Here njega is the genitive (and also accusative) form of the pronoun on.

Because pravokutnik and kvadrat are both masculine nouns, njega could in principle refer to either one, depending on context. In a real situation, the surrounding context would usually make the reference clear.

Yes, that is also possible.

Croatian often places short clitics like je in second position, so after pa you get:

• pa je učiteljica nacrtala...

But you can also have a different structure in another sentence or context, such as:

• Učiteljica je nacrtala...

Both are normal. The exact placement depends on what comes first in the clause and on standard clitic position rules.

Yes. In pravokutnik je ispao širi od kvadrata, the subject is pravokutnik.

You can tell because:

• it is in the nominative
• the participle ispao agrees with it in masculine singular

So the structure is essentially:

• pravokutnik = subject
• je ispao = past tense verb
• širi od kvadrata = complement

Yes, grammatically it can, because Croatian does not have articles.

Whether English should use a square or the square depends on the situation. In this sentence, since it sounds like a specific drawing exercise with a rectangle and a square, English would usually say the square. But the Croatian itself does not mark that directly with an article.