Matična ploča i čvrsti disk su u laptopu.

Because the subject is plural.

The sentence has two things:

• matična ploča = motherboard
• čvrsti disk = hard drive

They are linked by i = and, so together they form a plural subject: the motherboard and the hard drive.

That is why Serbian uses su = are, not je = is.

• ploča je = the board is
• disk je = the disk is
• ploča i disk su = the board and the disk are

Laptopu is in the locative singular.

After the preposition u when it means in or inside, Serbian usually takes the locative:

• u laptopu = in the laptop
• u kući = in the house
• u gradu = in the city

The base form is laptop. In the locative singular, many masculine nouns take -u:

• laptop → u laptopu
• grad → u gradu

So u laptopu literally means in the laptop.

Because Serbian nouns change form after prepositions depending on their grammatical role.

In English, in the laptop keeps laptop unchanged. In Serbian, the noun must go into the correct case. Since u here expresses location, it requires the locative, so:

• wrong: u laptop
• correct: u laptopu

This is one of the biggest differences from English: Serbian uses case endings where English often uses only word order and prepositions.

Literally, matična ploča means something like mother board, which matches the English term motherboard.

Breakdown:

• matična = maternal / main / mother-related
• ploča = board / plate

As a set phrase in computing, matična ploča is the normal Serbian word for motherboard.

Also notice agreement:

• ploča is feminine
• so the adjective is feminine too: matična

Because čvrsti is an adjective describing disk, and it must agree with it.

• disk is a masculine singular noun
• so the adjective is also masculine singular: čvrsti

This phrase means hard drive or literally solid/firm disk.

You may also hear tvrdi disk in Serbian. In everyday language, both can appear, but čvrsti disk is a standard and understandable expression.

Because adjectives in Serbian must agree with the noun in gender, number, and case.

Here:

• ploča is feminine singular nominative → matična ploča
• disk is masculine singular nominative → čvrsti disk

So the adjective endings are different because the nouns they describe are different.

Very roughly:

• feminine nominative singular often ends in -a
• masculine nominative singular often ends in a consonant, and the adjective often ends in -i

I means and.

So:

• matična ploča i čvrsti disk = the motherboard and the hard drive

Be careful with pronunciation:

• Serbian i is pronounced like ee in see
• but as a word, i still means and

Because Serbian does not have articles like English a/an and the.

So:

• matična ploča can mean a motherboard or the motherboard
• čvrsti disk can mean a hard drive or the hard drive
• u laptopu = in a laptop / in the laptop

The exact meaning depends on context. If the learner already knows which laptop or which components are being talked about, English may translate it with the.

The given word order is natural, but Serbian word order is more flexible than English.

Normal version:

• Matična ploča i čvrsti disk su u laptopu.

You could also say:

• U laptopu su matična ploča i čvrsti disk.

This version puts emphasis first on the location: In the laptop are the motherboard and the hard drive.

Because Serbian uses case endings, word order can move more freely than in English, though not completely freely in every context.

The letter č is pronounced roughly like ch in chocolate, but usually a bit firmer.

So:

• čvrsti starts with a ch sound
• č is different from c, which is pronounced like ts

For an English speaker:

• č ≈ ch
• c ≈ ts

So čvrsti is approximately CHVR-stee, though the exact Serbian pronunciation is a bit sharper.

Yes. It is a loanword used in Serbian.

Serbian often borrows modern technical vocabulary, especially for computers and electronics. Even borrowed nouns usually get Serbian case endings, which is exactly what happens here:

• base form: laptop
• locative after u: u laptopu

So although the word comes from English, it behaves like a normal Serbian noun in the sentence.