Learn Hardcore Croatian: Prema novom zakonu, plastika se mora bolje reciklirati. - According to the new law, plastic has to be recycled better.

The preposition prema requires the dative case, so novi zakon (nominative = the new law) changes to novom zakonu (dative = to/according to the new law).

Nominative: novi zakon – the new law
Dative: novom zakonu – to/according to the new law

So:
Prema novom zakonu = According to the new law

Why is there a comma after zakonu?

The comma separates the introductory prepositional phrase from the main clause.

Prema novom zakonu, = According to the new law, (introductory part)
plastika se mora bolje reciklirati. = main clause

In Croatian, it is common (and stylistically good) to use a comma after a longer introductory phrase like Prema novom zakonu. It’s very similar to English punctuation in this case.

What exactly does mora mean, and how is it formed?

Mora is the 3rd person singular present tense of the verb morati = to have to / must.

moram – I must / have to
moraš – you (sg.) must
mora – he/she/it must
moramo – we must
morate – you (pl.) must
moraju – they must

Here, the subject is plastika (3rd person singular), so the verb is mora:

Plastika se mora bolje reciklirati.
= Plastic must be recycled better.

What is the purpose of se in plastika se mora bolje reciklirati? Is it reflexive?

In this sentence, se is not reflexive in the sense of doing something to oneself. It is used to form the impersonal/passive-like construction, often called the reflexive passive or impersonal se-construction.

Plastika se mora reciklirati.
Literally: Plastic must recycle itself
Real meaning: Plastic must be recycled.

So se here:

removes the focus from who does the action, and
makes the sentence more general, like the English must be recycled.

It’s a very common way in Croatian to express general or passive meanings.

Why is it reciklirati and not something like reciklirana or reciklirati se?

Reciklirati is the infinitive form of the verb = to recycle.

The structure here is:

morati (must/have to) + infinitive (reciklirati)

So:

mora reciklirati = must recycle / must be recycled (with se making it passive-like)

You could say:

Plastika mora biti bolje reciklirana.
= Plastic must be better recycled.

That uses biti (to be) + passive participle reciklirana.
Both are correct, but se reciklirati is very natural and common in everyday language.

Can the word order change? For example, are these correct: Plastika se mora bolje reciklirati, Mora se plastika bolje reciklirati, Plastika mora biti bolje reciklirana?

Yes, Croatian allows flexible word order, though each version can have a slightly different emphasis.

All of these are grammatically correct:

Plastika se mora bolje reciklirati.
Neutral, natural order. Focus fairly balanced.
Mora se plastika bolje reciklirati.
Slightly emphasizes the necessity (mora) at the start.
Plastika mora biti bolje reciklirana.
Uses the biti + participle passive form. More explicit passive, can sound a bit more formal or written.

The original sentence with se reciklirati sounds perfectly normal in everyday speech and writing.

How does bolje work here, and why not bolja or više?

Bolje is the comparative form of the adverb dobro (well):

dobro = well
bolje = better (in the sense of more well)

It modifies the verb reciklirati (to recycle), so we need an adverb, not an adjective:

bolje reciklirati = to recycle better

Bolja is an adjective (feminine singular) meaning better as in a better thing:

bolja plastika = better plastic

Više means more, usually in quantity or degree:

više reciklirati = to recycle more (a larger amount)

So the choice:

bolje reciklirati = recycle in a better way / more efficiently
više reciklirati = recycle a larger amount / more often

The sentence is about quality/efficiency, so bolje is correct.

Why is it novom zakonu and not novi zakon? How does the adjective nov change?

Because prema requires the dative case, both the noun and the adjective must be in the dative masculine singular.

Base form (nominative):

novi zakon – the new law

Dative singular masculine:

novom zakonu – to the new law / according to the new law

Adjective nov (new), masculine singular:

Nominative: novi
Dative: novom

Noun zakon (law), masculine singular:

Nominative: zakon
Dative: zakonu

So prema novom zakonu is required by the preposition prema.

Can prema also mean towards? How do we know which meaning it has here?

Yes, prema has two common meanings:

according to (with abstract things like laws, rules, opinions)
- Prema novom zakonu = According to the new law
towards / in the direction of (with physical movement)
- Idem prema gradu. = I’m going towards the town.

In your sentence:

The object is novom zakonu (an abstract thing, a law),
The rest of the sentence talks about an obligation (plastika se mora bolje reciklirati),

So according to is the only natural interpretation here, not physical direction.

Is plastika singular or plural here? How would you say plastics in Croatian?

Plastika here is singular, feminine, and it acts as a mass noun, like English plastic when you mean the material in general.

plastika se mora reciklirati = plastic must be recycled

If you want to talk about different types of plastics, you can use:

plastike – plural of plastika
e.g. različite plastike = different plastics

But in general environmental or legal statements, Croatian typically uses the singular plastika as a mass noun, just like in this sentence.