Learn Hardcore Croatian: Učiteljica objašnjava da svaka vrsta rečenice ima svoja pravila pravopisa. - The teacher female explains that each type of sentence has its own spelling rules.

It ends in -ica, which is a common feminine ending (e.g. učitelj – male teacher, učiteljica – female teacher).
In this sentence it is in the nominative singular because it is the subject of the sentence – the one doing the explaining.

Croatian does not use articles like the/a, so učiteljica here corresponds to the teacher or a teacher in English, depending on context.

What exactly does objašnjava mean, and why isn’t it objasni?

Objašnjava means (she) explains / is explaining. Grammatically:

It is 3rd person singular present tense of the verb objašnjavati (to explain, imperfective).
Croatian distinguishes aspect:
- objašnjavati – imperfective, ongoing/repeated action: is explaining, explains
- objasniti – perfective, completed, one‑time action: to explain (once, fully)

In the present tense, you normally use the imperfective verb for an action happening right now or generally:

Učiteljica objašnjava… – The teacher is explaining / explains…

If you used the perfective in the present (objasni), it would usually refer to the future (something like “will explain” or “when she explains”), not what’s happening right now.

What is the function of da in this sentence?

Here da is a conjunction meaning that, introducing a subordinate (embedded) clause that functions as the object of objašnjava.

Main clause: Učiteljica objašnjava – The teacher explains
Subordinate clause: da svaka vrsta rečenice ima svoja pravila pravopisa – that every kind of sentence has its own spelling rules

So the teacher explains what? → that every kind of sentence has its own spelling rules.

This use of da is very common and directly corresponds to English that in sentences like:
She says that… / She explains that… / I think that…

Why is it svaka vrsta rečenice and not something like svaka rečenica?

Svaka vrsta rečenice literally means every type/kind of sentence.

svaka – every/each, feminine singular, matches vrsta
vrsta – type, kind, feminine singular noun
rečenice – of (a) sentence, genitive singular of rečenica

The expression vrsta rečenice is a set phrase in grammar, meaning a category of sentence (e.g. declarative, interrogative, imperative), not an individual sentence.

If you said svaka rečenica it would mean every sentence, referring to individual sentences, not to types of sentences.

Why is rečenice in the form rečenice and not rečenica or rečenicu?

Rečenice here is genitive singular of rečenica (sentence).

The pattern vrsta + genitive is very common:

vrsta rečenice – type of sentence
vrsta voća – kind of fruit
vrsta glagola – type of verb

So rečenice is in the genitive because it is dependent on (governed by) vrsta and means “type of sentence” (literally “type of sentence‑of”).

Why is the verb ima singular when we’re talking about “every kind of sentence”? Could it be imaju?

The verb must agree with the grammatical subject, which is svaka vrsta rečenice.

vrsta is singular (one type), so the whole phrase svaka vrsta rečenice is treated as singular.
Therefore the verb is ima (3rd person singular), not imaju (3rd person plural).

This is similar to English:

Every type of sentence has its own rules.
(You say has, not have.)

So imaju would be ungrammatical here.

What does svoja mean, and how is it different from njena or njegova?

Svoja is the reflexive possessive adjective meaning its own / her own / his own, depending on context.

Here it refers back to the subject svaka vrsta rečenice:

svaka vrsta rečenice ima svoja pravila
= each kind of sentence has its own rules

Key points:

Reflexive vs. non‑reflexive
- svoj, svoja, svoje… – used when the possessor is the subject of the sentence.
- njegov, njegova… – his / its (masc)
- njezin, njezina… – her / its (fem)
Correct:
- Svaka vrsta rečenice ima svoja pravila. – Each type of sentence has its own rules.
Agreement in gender and number
- pravila – neuter plural
- svoja – neuter plural form of svoj, agreeing with pravila

Note that svoja can also be feminine singular (depending on context), but here it is neuter plural, matching pravila.

What does pravila pravopisa literally mean, and why is pravopisa in that form?

Pravila pravopisa literally means rules of spelling/orthography.

pravila – rules, nominative (or accusative) neuter plural of pravilo
pravopisa – of orthography/spelling, genitive singular of pravopis

The genitive pravopisa tells you what kind of rules:

pravila igre – rules of the game
pravila gramatike – rules of grammar
pravila pravopisa – rules of spelling

In the sentence, pravila pravopisa as a whole is the object of ima (has).

Why is there no article like “the” or “a” anywhere? How would I know if it’s “the teacher” or “a teacher”?

Croatian has no articles (no equivalents of English a/an/the), so nouns appear without them:

učiteljica – can mean a teacher or the teacher
svaka vrsta rečenice – every kind of sentence
pravila pravopisa – spelling rules / the spelling rules

Whether you interpret it as a teacher or the teacher depends entirely on context, not on any word in the sentence. In most natural translations to English here, you would say The teacher explains that….

Could I change the word order inside the da‑clause, for example put svoja pravila earlier?

Basic, neutral word order is:

svaka vrsta rečenice ima svoja pravila pravopisa
Subject – Verb – Object

Croatian does allow word‑order variation for emphasis, but you must be careful. For example:

svaka vrsta rečenice svoja pravila pravopisa ima
– possible, but sounds more marked/emphatic; it emphasizes svoja pravila pravopisa.

You usually do not split fixed combinations like pravila pravopisa or separate svoja far from pravila. So, as a learner, it’s safest to keep:

Subject – Verb – Object: svaka vrsta rečenice ima svoja pravila pravopisa.

Is a comma ever needed before da here, like Učiteljica objašnjava, da…?

In this sentence, standard modern Croatian does not use a comma before da:

Učiteljica objašnjava da svaka vrsta rečenice ima svoja pravila pravopisa.

The da‑clause here is a direct object clause of objašnjava, and it is normally written without a comma in contemporary usage.

So you should write it exactly as given, without a comma before da.