Čeona lampa, kabanica i čuturica su u rancu.

Because the subject is plural: it is a list of three things — čeona lampa, kabanica i čuturica.

In Serbian, just like in English, a compound subject joined by i (and) normally takes a plural verb.

• je = is
• su = are

So:

• Lampa je u rancu. = The lamp is in the backpack.
• Lampa i kabanica su u rancu. = The lamp and the raincoat are in the backpack.

The three listed items are in the nominative, because they form the subject of the sentence:

• čeona lampa
• kabanica
• čuturica

The word rancu is in the locative singular, because it follows u in the meaning of location:

• u rancu = in the backpack

So the structure is:

• [Subject in nominative] + su + [location phrase]

Because u can take different cases depending on meaning.

• u + locative = being in something, location
• u + accusative = going into something, direction/movement

Here the sentence describes where the items are, not where they are going, so Serbian uses the locative:

• u rancu = in the backpack

Compare:

• Stvari su u rancu. = The things are in the backpack.
• Stavljam stvari u ranac. = I am putting the things into the backpack.

The noun ranac changes like this:

• nominative: ranac
• accusative: ranac
• locative: rancu

Literally, it means something like forehead/front lamp, and in natural English it corresponds to headlamp or head torch.

• čeona is an adjective related to čelo = forehead
• lampa = lamp

So čeona lampa is a lamp worn on the head.

Also notice that čeona agrees with lampa:

• lampa is feminine singular
• therefore the adjective is also feminine singular nominative: čeona

Yes. All three are feminine singular nouns, and one clue is that they all end in -a:

• lampa
• kabanica
• čuturica

That said, the verb is still plural because the sentence is talking about all three items together.

Also, only čeona modifies lampa. It does not describe the other two nouns. The list is:

• čeona lampa
• kabanica
• čuturica

not:

• čeona lampa
• čeona kabanica
• čeona čuturica

Because Serbian has no articles. There is no direct equivalent of English a/an or the that must appear before nouns.

So kabanica can mean:

• a raincoat
• the raincoat

The exact meaning depends on context.

If Serbian wants to be more specific, it can use words like:

• ova kabanica = this raincoat
• ta kabanica = that raincoat
• jedna kabanica = a/one raincoat

But in a normal sentence, bare nouns are completely natural.

Because in a simple list, Serbian normally does not put a comma before i (and), just like standard English usually does without the Oxford comma.

So:

• Čeona lampa, kabanica i čuturica

is the normal way to write:

• headlamp, raincoat and canteen

You separate earlier items with commas, but usually not the final i in a simple series.

Serbian word order is fairly flexible, but su is a clitic and clitics usually go in second position in the sentence or clause.

In this sentence, the whole subject phrase counts as the first unit:

• Čeona lampa, kabanica i čuturica | su | u rancu

So su comes right after that first unit.

You can also change the order for emphasis:

• U rancu su čeona lampa, kabanica i čuturica.

This version emphasizes the location first: In the backpack are...

Both are correct, but the original is a very natural neutral sentence.

The letter č is pronounced roughly like the ch in church, but usually a bit firmer and more clearly articulated than in English.

So:

• Čeona starts with a ch sound
• čuturica also starts with that same ch sound

A few quick pronunciation notes:

• č = a hard ch sound
• c in Serbian is different: it sounds like ts
• r in rancu is a tapped or trilled r, not the English r
• each written vowel is pronounced clearly: a, e, i, o, u

Approximate pronunciations:

• Čeona ≈ CHEH-oh-na
• čuturica ≈ CHOO-too-ree-tsa
• rancu ≈ RAHN-tsoo

These are only approximations, but they are a helpful starting point.

Not necessarily.

The ending -ica is very common in Serbian and can do different things. It often appears in:

• feminine nouns
• diminutives
• lexicalized words where speakers may not strongly feel any diminutive meaning

In this sentence:

• kabanica is simply the normal word for raincoat
• čuturica may historically or stylistically feel somewhat diminutive in some contexts, but in practice it is also just a common noun for a flask/canteen

So it is better not to assume that every -ica word means little X. Sometimes it does, sometimes it does not.

Yes, in many contexts you could. Both ranac and ruksak can mean backpack.

So you could also say:

• Čeona lampa, kabanica i čuturica su u ruksaku.

The grammar stays the same:

• u ruksaku = locative after u for location

The choice between ranac and ruksak is mostly a vocabulary choice, and both are common.