Learn Hardcore Croatian: Možda će se on pojaviti kasnije.

a reflexive pronoun, but in verbs like pojavitI se it is mostly part of the verb itself, not a real reflexive meaning like to wash oneself.

You very rarely use pojavitI without se in modern Croatian.
If you drop se, it usually sounds wrong or at least very unusual:

✅ On će se pojaviti. = He will appear.
❌ On će pojaviti. – feels incomplete / incorrect in normal speech.

So: memorize the verb as a whole: pojavitI se = to appear.

Why is the word order Možda će se on pojaviti, and not Možda on će se pojaviti?

Croatian has a strong rule about clitics (short unstressed words like će, se, mi, ga, li).
They usually have to stand in second position in the clause.

In the sentence:

Možda = first stressed word in the clause
će se = clitic cluster (će
- se)
on = full pronoun (stressed word)
pojaviti = main verb

So the clitics go right after the first stressed word:

✅ Možda će se on pojaviti kasnije.

The version Možda on će se pojaviti breaks the clitic rule, because će se is no longer in second position:

❌ Možda on će se pojaviti kasnije. – ungrammatical.

Can I drop on and just say Možda će se pojaviti kasnije?

Yes, absolutely.

Croatian normally omits subject pronouns when the subject is clear from context. Since će already shows person/number (3rd person singular), on is not required:

✅ Možda će se pojaviti kasnije. = Maybe he will show up later.
✅ Možda će se on pojaviti kasnije. = Maybe he will show up later (extra emphasis on he).

Using on here gives emphasis or contrast, something like:

Maybe *he (as opposed to someone else) will appear later.*

Could the sentence also be On će se možda pojaviti kasnije? Does it mean the same?

Yes, that sentence is correct, but the emphasis changes slightly.

Možda će se on pojaviti kasnije.
- možda is first => you are primarily stating uncertainty.
- Roughly: Maybe he will appear later.
On će se možda pojaviti kasnije.
- on is first => the subject he is more in focus.
- It can sound more like: He might appear later (I’m talking about him).

In everyday speech, both are fine, and the difference is subtle.
Both communicate the same basic idea: it is uncertain whether he will appear later.

Can I put se after pojavitI, like Možda će on pojaviti se kasnije?

No. In standard Croatian, the reflexive se is also a clitic, and it must:

stand near the beginning of the clause (in the clitic cluster),
not normally come after the infinitive in this structure.

So:

✅ Možda će se on pojaviti kasnije.
✅ On će se pojaviti kasnije.
✅ On će se možda pojaviti kasnije.
❌ Možda će on pojaviti se kasnije.

There is another allowed pattern where će comes after the infinitive; then se also follows it:

✅ On će se pojaviti.
✅ On će se pojaviti kasnije.
✅ On će se kasnije pojaviti.
✅ On će se možda pojaviti.
✅ On će se pojaviti možda kasnije.
✅ On će se pojaviti, možda kasnije.

But pojavitI se as [infinitive + se] usually appears when nothing is between the two, or when the clitic cluster is earlier in the sentence.
Pojaviti se at the very end (as in pojavit će se) is also fine:

✅ On će se pojaviti.
✅ On će se pojaviti kasnije.
✅ On će se možda pojaviti kasnije.

Is there any difference between Možda će se on pojaviti kasnije and Možda se on pojavi kasnije?

Yes, there is a difference in tense and nuance:

Možda će se on pojaviti kasnije.
- Future I (će + infinitive)
- Neutral, standard way to talk about a future possibility:
  Maybe he will show up later.
Možda se on pojavi kasnije.
- Present tense used with a future meaning, often for a more tentative, hypothetical or hopeful tone, sometimes a bit more colloquial.
- Feels like: Maybe he ends up appearing later / Maybe he happens to show up later.

Both are understandable; the future construction with će is safer and more textbook-standard.

Do I need a comma after Možda: Možda, će se on pojaviti kasnije?

No, you should not put a comma there.

Možda is just an adverb inside a single clause, not a separate clause or a parenthetical expression. So:

✅ Možda će se on pojaviti kasnije.
❌ Možda, će se on pojaviti kasnije.

You would only use a comma with možda if it starts a separate clause in a longer sentence, e.g.:

Ne znam hoće li doći, možda će se pojaviti kasnije.
(Here the comma separates two clauses, not the word možda itself.)

What is the difference between možda and može biti in this context?

Both express possibility, but they are not always interchangeable:

možda = maybe, perhaps
- Short, very common, used before the verb:
  - Možda će se on pojaviti kasnije.
    = Maybe he will show up later.
može biti literally = it can be / it may be
- Often used as a separate comment:
  - Može biti da će se on pojaviti kasnije.
    = It may be that he will show up later.
  - Or simply: Može biti. = Possibly / Could be.

You normally would not say:

❌ Može biti će se on pojaviti kasnije.

You need da to introduce the clause:

✅ Može biti da će se on pojaviti kasnije.

Is there any difference between kasnije and poslije here?

In this sentence, kasnije and poslije are very close in meaning:

kasnije = later (a bit more neutral here)
poslije = afterwards / later

You can say:

Možda će se on pojaviti kasnije.
Možda će se on pojaviti poslije.

In most everyday contexts they are interchangeable.
Kasnije can feel a bit more like later on (sometime after now), while poslije can be a bit more concrete or tied to a previous event, but the difference is subtle and often not important in casual speech.