Moja sestra se smijala kad je majmun uzeo bananu.

Because moj changes to match the noun it describes.

Sestra is:

• feminine
• singular
• nominative here

So the correct form is moja.

Compare:

• moj brat = my brother
• moja sestra = my sister
• moje dijete = my child

Here se is part of the verb smijati se, which means to laugh.

So you should learn smijati se as a whole verb, not just smijati by itself in this meaning.

In this sentence, se does not literally mean herself. It is just a normal part of the Croatian verb.

The dictionary form is smijati se.

Smijala is a past-tense form built from that verb. More specifically, it is the feminine singular past participle, used because the subject is moja sestra.

Related forms:

• smijao = masculine singular
• smijala = feminine singular
• smijalo = neuter singular
• smijali = masculine mixed plural
• smijale = feminine plural

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

The subject here is sestra, which is feminine singular, so the verb form is smijala.

If the subject were different, the form would change:

• Moj brat se smijao
• Moja sestra se smijala
• Moje sestre su se smijale

That is a very common learner question.

Croatian past tense usually uses an auxiliary plus a past participle:

• Majmun je uzeo bananu

But with reflexive verbs like smijati se, in the 3rd person singular, Croatian normally does not use je here.

So the normal form is:

• Ona se smijala

not:

• Ona je se smijala
• Ona se je smijala

In other persons, the auxiliary does appear:

• Ja sam se smijala
• Ti si se smijao
• Mi smo se smijali

Because je is a clitic. Croatian clitics usually go in the second position in their clause.

In the clause kad je majmun uzeo bananu:

• kad comes first
• the clitic je goes right after it

So this order is normal:

• kad je majmun uzeo bananu

A learner may expect something like kad majmun je uzeo bananu, but that is not the usual neutral Croatian order.

The base form is uzeti, meaning to take.

Uzeo is the masculine singular past participle of uzeti. Croatian verbs often change their stem in past forms, so the past participle does not always look very close to the infinitive.

Useful forms:

• uzeti = infinitive
• uzeo = masculine singular
• uzela = feminine singular
• uzelo = neuter singular
• uzeli = plural

Here it is uzeo because majmun is masculine singular.

This is about aspect, which is very important in Croatian.

• uzeti / uzeo = perfective, a completed action
• uzimati / uzimao = imperfective, ongoing or repeated action

In this sentence, the monkey’s taking of the banana is presented as one completed event, so uzeo is the natural choice.

This also fits the overall scene:

• se smijala = background action
• uzeo = single event that happened during it

So the sentence has a very typical Croatian aspect contrast.

Because bananu is the direct object, so it is in the accusative case.

The noun banana is a feminine noun ending in -a, and in the accusative singular it becomes bananu.

So:

• banana = nominative
• bananu = accusative

Here the monkey is doing something to the banana, so the accusative is required.

Yes.

Both kad and kada mean when.

• kad is shorter and very common in everyday language
• kada is a bit fuller in form and can sound slightly more formal or careful

So these are both fine:

• kad je majmun uzeo bananu
• kada je majmun uzeo bananu

Croatian word order is fairly flexible, but clitics such as se and je still have special placement rules.

The given sentence is a neutral, natural order:

• Moja sestra se smijala kad je majmun uzeo bananu.

You could also say:

• Kad je majmun uzeo bananu, moja sestra se smijala.

That changes the focus a little, but the meaning stays basically the same.

What usually does not change freely is the position of clitics:

• se
• je

They still need to stay in their normal clitic position.