Learn Hardcore Croatian: Slobodno mi reci svoje mišljenje.

Molim te, reci mi svoje mišljenje. = Please tell me your opinion.
Slobodno mi reci svoje mišljenje. = Don’t hesitate / You’re allowed to / It’s okay to tell me your opinion.

They can be combined:

Molim te, slobodno mi reci svoje mišljenje.
= Please, feel free to tell me your opinion.

What part of speech is Slobodno here, and could it be placed somewhere else in the sentence?

Here Slobodno is an adverb, modifying the verb reci (say, tell).

You can move it around quite freely in this short sentence; the meaning stays the same, with only tiny differences in emphasis:

Slobodno mi reci svoje mišljenje. (neutral, very common)
Reci mi slobodno svoje mišljenje. (slight emphasis at the end)
Reci mi svoje mišljenje slobodno. (less common; slobodno sounds more like an afterthought)

All of these are grammatically correct. The first is the most natural and standard.

Why is it mi reci and not reci mi? Can I say Reci mi svoje mišljenje instead?

You can say both:

Slobodno mi reci svoje mišljenje.
Slobodno reci mi svoje mišljenje.

Both are grammatical. Native speakers actually tend to prefer Slobodno mi reci… because mi is an enclitic (an unstressed short word) and Croatian likes to place enclitics very early in the sentence, usually in the second position.

Some typical variants:

Slobodno mi reci svoje mišljenje. ✅ (very natural)
Reci mi slobodno svoje mišljenje. ✅
Slobodno reci mi svoje mišljenje. ✅ but sounds a bit less smooth

So Reci mi svoje mišljenje (without slobodno) is also perfectly correct and common:

Reci mi svoje mišljenje. = Tell me your opinion.

What does mi mean here, and which case is it?

Mi in this sentence is the dative form of the 1st person singular pronoun ja (I).

Nominative: ja = I
Dative: meni / mi = to me

In this context, mi means to me:

Reci mi… = Tell me… (literally: Say to me…)

So you have:

Slobodno mi reci svoje mišljenje.
literally: Freely to-me say your opinion.

Why is it reci and not reći? Are these two different words?

They are forms of the same verb.

reći is the infinitive form: to say / to tell
reci is the imperative (second person singular): say! / tell!

So:

Želim ti nešto reći. = I want to tell you something. (infinitive)
Reci mi nešto. = Tell me something. (imperative)

In your sentence, reci is a command/request form addressed to ti (you, singular informal):

Slobodno mi reci svoje mišljenje.
= (You) feel free to tell me your opinion.

What is the difference between reci and kaži? Can I say Slobodno mi kaži svoje mišljenje?

Reci and kaži are both imperative forms meaning say / tell.

reci – from reći, slightly more neutral/formal
kaži – from kazati, often feels a bit more conversational

In this sentence you can use either:

Slobodno mi reci svoje mišljenje. ✅
Slobodno mi kaži svoje mišljenje. ✅

Both mean Feel free to tell me your opinion.
In everyday speech, kaži is extremely common, especially in some regions.
In writing and more neutral standard Croatian, reci is maybe a bit more typical, but both are fine.

Which case is svoje mišljenje in, and how does the agreement work?

Mišljenje (opinion) is a neuter noun, and here it’s in the accusative singular, because it is the direct object of the verb reci.

reč(i) + what? → (svoje) mišljenje → accusative object

Svoje is a possessive reflexive pronoun that must agree with the gender, number, and case of the noun it modifies:

Nominative neuter sg.: svoje mišljenje
Accusative neuter sg.: svoje mišljenje (same form as nominative for neuter)

So both svoje and mišljenje are:

gender: neuter
number: singular
case: accusative

Why is it svoje mišljenje and not tvoje mišljenje?

Svoje is the reflexive possessive pronoun, used when the possessor is the same as the subject of the sentence.

Here the (implied) subject is ti (you):

(Ti) slobodno mi reci svoje mišljenje.
= (You) feel free to tell me your (own) opinion.

Because the opinion belongs to you (the subject ti), Croatian uses svoje.

You could technically say:

Slobodno mi reci tvoje mišljenje.

but this sounds less natural and can be interpreted as your (not necessarily your own, could be someone else’s that you hold), or it just feels redundant/weird here. Native speakers overwhelmingly prefer svoje mišljenje in this context.

General rule:

If the possessor = subject → prefer svoj / svoja / svoje instead of moj / tvoj / njegov ….

Can I drop svoje and just say Slobodno mi reci mišljenje?

Grammatically, you can say Slobodno mi reci mišljenje, but it sounds unnatural and incomplete in most contexts. Without svoje (or some other determiner), mišljenje is very bare, like saying “tell me opinion” in English.

More natural options:

Slobodno mi reci svoje mišljenje. ✅
Slobodno mi reci svoje iskreno mišljenje. ✅
Slobodno mi reci svoje pravo mišljenje. ✅

If context is extremely clear (e.g., you were just talking about your opinion vs mine), then reći mišljenje might pass, but in isolation, the version with svoje is the normal one.

How formal or informal is this sentence, and how would I say it more formally?

Slobodno mi reci svoje mišljenje. is addressed to ti (informal you, singular). It’s friendly, polite, and informal.

A more formal version (to one person, using vi) is:

Slobodno mi recite svoje mišljenje.
(reci → recite, for vi)

Formality levels:

Informal (friends, family, peers):
Slobodno mi reci svoje mišljenje.
Formal or polite (strangers, elders, business context):
Slobodno mi recite svoje mišljenje.

You can also add molim to sound extra polite:

Molim vas, slobodno mi recite svoje mišljenje.

Do we need to use the subject pronoun ti here? Where would it go if we include it?

The subject pronoun ti is not required because the verb form reci already shows it’s 2nd person singular.

Standard, natural:

Slobodno mi reci svoje mišljenje. ✅

If you do include ti, it usually adds emphasis (like you in English):

Ti mi slobodno reci svoje mišljenje. (emphasis on you)
Ti mi reci svoje mišljenje slobodno. (also possible, but slightly less smooth)

Croatian typically omits subject pronouns unless there’s a reason to stress them, so the original version without ti is the most neutral and common.

How would I negate this idea if I want to say something like “Don’t hesitate to tell me your opinion” in Croatian?

If you want to keep close to the idea “Don’t hesitate to tell me your opinion”, you don’t just negate reci; you change the verb. Common, natural options:

Nemoj se ustručavati reći mi svoje mišljenje.
= Don’t hesitate to tell me your opinion.

You can also combine it with slobodno:

Slobodno mi reci svoje mišljenje, nemoj se ustručavati.
= Feel free to tell me your opinion, don’t hesitate.

If you directly negate reci, you get a different meaning:

Nemoj mi reći svoje mišljenje.
= Don’t tell me your opinion. (the opposite of what you want)

So for “Don’t hesitate”, use nemoj se ustručavati (or similar expressions), not nemoj reći.

Can Slobodno be used on its own in conversation, and does it keep the same meaning?

Yes. Slobodno is very often used by itself in everyday conversation to mean things like:

Go ahead.
Feel free.
Help yourself.
Be my guest.

Examples:

Someone asks: Mogu li sjesti ovdje? (Can I sit here?)
You: Slobodno. (Go ahead.)
Someone reaches for food at your place and hesitates:
You: Slobodno, posluži se. (Go ahead, help yourself.)

So in your sentence, Slobodno mi reci svoje mišljenje fits into this pattern: Slobodno = (Go ahead and) feel free.