Learn Hardcore Croatian: Učimo osnovne riječi svaki dan.

The ending -imo in učimo clearly means we (first person plural), so the subject mi (we) is left out as unnecessary: Učimo osnovne riječi svaki dan.

Could učimo also mean let’s learn?

Yes. Učimo can be:

Present tense: (Mi) učimo osnovne riječi svaki dan. – We (habitually) learn basic words every day.
1st person plural imperative (let’s …): Učimo osnovne riječi! – Let’s learn basic words!

The meaning is decided by context and punctuation.

With something like svaki dan (every day), it’s clearly a normal present tense.
With an exclamation mark and no time expression, it often sounds like an encouragement or instruction: Učimo! = Let’s learn!

Why is there no word for are (like in “We are learning”)?

Croatian does not form the present tense with a separate auxiliary like English am/are/is in the continuous (progressive).

English: We are learning basic words every day.
Croatian: Učimo osnovne riječi svaki dan.

The simple present in Croatian covers both:

We learn (habitual)
We are learning (right now / current activity)

If you really want to stress “right now”, you can add an adverb:
Sada učimo osnovne riječi. – We are learning basic words now.

Why is osnovne riječi in that form? What are the gender and case?

riječ (word) is a feminine noun.
osnovan / osnovna / osnovno means basic, and here we have osnovne, the feminine plural form.

In the sentence, osnovne riječi is the direct object of učimo, so it is in the accusative plural. For this noun, nominative plural and accusative plural look the same:

nominative plural: osnovne riječi (as the subject)
accusative plural: Učimo osnovne riječi. (as the object)

So here it is feminine accusative plural, with the adjective osnovne agreeing in gender, number, and case with riječi.

What is the singular form of riječi, and how does it decline?

The singular is riječ (word). Its main forms:

nominative singular: riječ – the word as subject
genitive singular: riječi – of the word
dative/locative singular: riječi – to / about the word
accusative singular: riječ – (I read) the word
instrumental singular: riječi – with the word

Plural:

nominative plural: riječi – words (subject)
accusative plural: riječi – words (object)

So in osnovne riječi, you are seeing the plural form.

Why is it osnovne riječi, not osnovna riječi or osnovne riječ?

Because the adjective must agree with the noun:

riječ – feminine singular → osnovna riječ – one basic word
riječi – feminine plural → osnovne riječi – basic words

So:

osnovna riječ – singular
osnovne riječi – plural

Mixing singular and plural (like osnovna riječi or osnovne riječ) would be ungrammatical.

What exactly does svaki dan mean grammatically, and which case is it?

svaki dan literally is every day:

svaki – an adjective meaning every, each (masculine singular nominative/accusative)
dan – day, a masculine noun

In time expressions like this, dan is in the accusative singular, but it looks the same as the nominative. So svaki dan is an accusative time expression meaning (on) every day, used without a preposition.

Example:

Učimo osnovne riječi svaki dan. – We learn basic words every day.

Can I also say svakog dana instead of svaki dan? Is there any difference?

Yes, both are correct and very common:

svaki dan – accusative
svakog dana – genitive

Meaning-wise, they are practically the same: every day.

Subtle differences:

svaki dan sounds a bit more neutral and straightforward.
svakog dana can sound slightly more emphatic or stylistically “fuller”, but in everyday speech they’re often interchangeable.

So you could also say:

Učimo osnovne riječi svakog dana. – We learn basic words every day.

Can I change the word order, for example: Svaki dan učimo osnovne riječi?

Yes. Croatian word order is flexible, and changes often reflect emphasis rather than grammar.

All of these are correct:

Učimo osnovne riječi svaki dan. – neutral: what do we do every day? We learn basic words.
Svaki dan učimo osnovne riječi. – emphasis on every day.
Osnovne riječi učimo svaki dan. – emphasis on basic words (as opposed to something else).

The core grammatical information comes from endings, not from word order.

How would I negate this sentence? How do I say We don’t learn basic words every day?

To negate a present tense verb in Croatian, you usually put ne directly in front of it:

Učimo osnovne riječi svaki dan. – We learn basic words every day.
Ne učimo osnovne riječi svaki dan. – We do not learn basic words every day.

The rest of the sentence stays the same.
Ne always comes before the main verb in this type of negation.

Is there any difference between učiti and naučiti in this context?

Yes, this is about aspect (imperfective vs. perfective):

učiti – imperfective, focuses on the process of learning, something ongoing or repeated.
- Učimo osnovne riječi svaki dan. – We are engaged in learning basic words every day.
naučiti – perfective, focuses on the completion or result of learning.
- Naučili smo osnovne riječi. – We (have) learned / we finished learning the basic words.

So your sentence correctly uses učiti to describe an ongoing, repeated activity.

How would I change the verb if I want to talk about other people: I, you, they?

Using učiti (to learn) in the present:

ja učim osnovne riječi svaki dan – I learn basic words every day
ti učiš osnovne riječi svaki dan – you (singular, informal) learn basic words every day
on/ona uči osnovne riječi svaki dan – he/she learns basic words every day
mi učimo osnovne riječi svaki dan – we learn basic words every day
vi učite osnovne riječi svaki dan – you (plural or formal) learn basic words every day
oni/one uče osnovne riječi svaki dan – they (masc./fem.) learn basic words every day

Usually you can omit the pronouns (ja, ti, on…) because the endings already show the person.

Does Croatian distinguish between We learn basic words every day and We are learning basic words every day?

Not in the same way English does. The Croatian present tense učimo can cover both:

We learn basic words every day. (habit / routine)
We are learning basic words every day. (ongoing project or process)

Context and additional words make the nuance clearer, but grammatically it is just the present tense:

Učimo osnovne riječi svaki dan.