U školskom dnevniku je upisano da sutra imamo kratki test iz hrvatskog.

It has been entered in the class register that tomorrow we have a short Croatian test.

Breakdown of U školskom dnevniku je upisano da sutra imamo kratki test iz hrvatskog.

• biti: to be
• imati: to have
• u: in
• hrvatski: Croatian

Questions & Answers about U školskom dnevniku je upisano da sutra imamo kratki test iz hrvatskog.

What does u školskom dnevniku mean, and why is it in that form?

It means in the school register / in the class record book.

Why that form:

• u = in
• after u (when it means location), Croatian normally uses the locative
• so:
  • školski dnevnik = the school register
  • u školskom dnevniku = in the school register

Both words change because the adjective must agree with the noun:

• školski → školskom
• dnevnik → dnevniku

Also, dnevnik here does not mean a personal diary. In a school context, it means the official class record book/register.

Why is it školskom dnevniku and not školski dnevnik?

Because Croatian nouns change form depending on their role in the sentence.

Here the phrase comes after u meaning in, so Croatian uses the locative case:

• base form: školski dnevnik
• locative: školskom dnevniku

The adjective and noun must match in:

• gender
• number
• case

So:

• masculine singular nominative: školski dnevnik
• masculine singular locative: školskom dnevniku