Learn Hardcore Croatian: Jedna prednost grupe je što smo motiviraniji, a jedna mana je buka u učionici. - One advantage of the group is that we are more motivated, and one disadvantage is the noise in the classroom.

prednost (advantage) is a feminine noun.
The number jedan (one) has different forms:
- jedan – masculine
- jedna – feminine
- jedno – neuter

So you need jedna prednost (one advantage), not jedan prednost.

Why is it jedna prednost grupe, with grupe and not grupa?

grupe is the genitive singular of grupa (group).

In Croatian, when you say "an advantage of something", you usually use prednost + genitive:

prednost grupe – the advantage of the group
prednost rada u paru – the advantage of working in pairs

So grupe answers "advantage of what?" and must be in the genitive. Using prednost grupa (nominative plural) would be wrong here.

What exactly is što doing in što smo motiviraniji? Isn’t što usually "what"?

što has two common roles:

As a question word / relative pronoun:
- Što radiš? – What are you doing?
As a subordinating conjunction meaning roughly “that”:
- Sviđa mi se što smo motiviraniji. – I like that we are more motivated.

In Jedna prednost grupe je što smo motiviraniji, što introduces a subordinate clause that explains the content of the advantage:

što smo motiviraniji ≈ that we are more motivated.

So here it’s not "what" but a conjunction similar to that in English.

Why is it što smo motiviraniji and not što mi smo motiviraniji?

The subject mi (we) is implied by the verb form smo (1st person plural of biti – to be), so it’s usually dropped:

mi smo = we are, but you normally just say smo once the subject is clear.

Croatian often omits subject pronouns because the verb ending already shows the person:

smo motiviraniji = (we) are more motivated.

You could say što mi smo motiviraniji, but it would sound strange and unnecessary in normal speech.

What form is motiviraniji, and why not something like više motivirani?

motiviraniji is the comparative form of the adjective motiviran (motivated):

motiviran – motivated
motiviraniji – more motivated

Croatian has morphological comparatives (changing the word itself) instead of always using više (more). Both are possible in many cases:

smo motiviraniji
smo više motivirani

Both can be understood as “we are more motivated”.
Using the comparative form motiviraniji is perfectly natural and slightly more compact.

Why is the word order što smo motiviraniji and not što motiviraniji smo?

In Croatian, short auxiliary verbs like sam, si, je, smo, ste, su are clitics, and they like to appear in the second position in the clause.

In the clause introduced by što:

što (= that) comes first,
smo (we are) must come very early, usually in second position,
motiviraniji comes after.

So što smo motiviraniji is the natural order.
što motiviraniji smo sounds wrong, because smo is pushed too far back.

Why is the conjunction a used before jedna mana, and not i or ali?

Croatian has several coordinating conjunctions:

i – and (simple addition)
ali – but (strong contrast, often unexpected)
a – and / while / whereas (milder contrast or comparison)

In a jedna mana je buka u učionici, a introduces another item that contrasts with the first one:

One advantage is X, and/whereas one disadvantage is Y.

Using:

i jedna mana… would sound like just adding another positive point.
ali jedna mana… puts stronger emphasis on opposition.

a is perfect here: it smoothly contrasts the advantage with the disadvantage.

Why is it jedna mana, not jedan mana?

Same gender-agreement rule as with prednost:

mana (disadvantage, flaw) is a feminine noun.
The numeral must match: jedna mana, not jedan mana.

So:

jedan problem (problem – masculine)
jedna mana (flaw/disadvantage – feminine)
jedno pitanje (question – neuter)

What’s the difference between mana and nedostatak?

Both can mean “disadvantage” / “weakness”, but there are nuances:

mana
- Often used for a flaw, drawback, negative side of something or someone.
- Quite common in everyday speech.
- Pairs nicely with prednost in set phrases:
  - prednosti i mane – pros and cons.
nedostatak
- More literally: lack, shortage, deficiency, but also used as disadvantage.
- Can sound a bit more neutral or formal in some contexts.

In this sentence, jedna mana matches very naturally with jedna prednost as "one advantage, one disadvantage".

Why is it buka u učionici, and why is učionici in that form?

učionici is the locative singular of učionica (classroom).

The preposition u (in) can take either locative or accusative, depending on meaning:

u
- locative = location (where?)
  - u učionici – in the classroom
u
- accusative = movement into (where to?)
  - u učionicu – into the classroom

Here we talk about where the noise is (location), so u učionici (locative) is correct.

Why is buka singular? In English we might say “the noise” or “noises” – does Croatian treat it differently?

buka is usually treated as a mass/uncountable noun in Croatian, similar to noise in English:

buka – noise (in general)
Mnogo je buke. – There is a lot of noise.

So buka u učionici = (the) noise in the classroom, talking about noise as a general phenomenon, not counting individual sounds.

You can use a plural buke in some contexts, but that usually implies types or instances of noise and is much less common in this kind of sentence.

Could you say Prednost grupe je što smo motiviraniji without jedna? What changes?

Yes, you can say:

Prednost grupe je što smo motiviraniji.

The difference:

Jedna prednost grupe… – one advantage of the group (implies there are several; you’re listing them).
Prednost grupe… – the advantage of the group (either the main one, or speaking more generally).

In your full sentence, using jedna for both prednost and mana makes it clear you’re naming one specific pro and one specific con from a list of possible ones.