Learn Hardcore Croatian: Ako si umorna, možeš biti kod kuće. - If you are tired, you can be at home. female

To a woman (2nd sg): Ako si umorna, možeš biti kod kuće.
To a man (2nd sg): Ako si umoran, možeš biti kod kuće.
To several people (mixed group or men): Ako ste umorni, možete biti kod kuće.
To several women: Ako ste umorne, možete biti kod kuće.

Is možeš biti the best verb here, or is možeš ostati more natural?

Both are correct, but the nuance differs:

možeš biti (kod kuće) = you can be at home (permission to be there; neutral).
možeš ostati (kod kuće) = you can stay at home (emphasizes staying instead of going out). In everyday speech, many would say Ako si umorna, možeš ostati kod kuće.

Why is it kod kuće and not u kući or just kući or doma?

kod kuće is the standard idiom for “at home.”
u kući = “in the house” (inside a house as a building), not necessarily your home.
kući without a preposition usually means “home(wards)” (direction): Idem kući = I’m going home. As “at home,” kući is heard colloquially in some regions, but standard is kod kuće.
doma = “at home”/“home” (very common colloquial/regional; widely understood): Biti/ostati doma.

What case is kuće and why?

Kuće is genitive singular. The preposition kod (“at/by [someone’s place]”) takes the genitive:

kod kuće (at home)
kod doktora (at the doctor’s)
kod prijatelja (at a friend’s place)

Where does si go? Can I say Ako umorna si or Si umorna?

No. Croatian clitics (like si, sam, je, etc.) prefer second position in their clause.

Correct: Ako si umorna, … (clitic is second in the clause)
Incorrect: Ako umorna si, …
Incorrect: Si umorna, … (clitic can’t be first)

Can I add ti for emphasis? Is Ako si ti umorna okay?

Yes. Ako si ti umorna, … is fine and emphasizes “you” (as opposed to someone else). Keep si in second position. Don’t say Ako ti si umorna (wrong clitic placement).

Can I use jesi instead of si? What’s the difference?

jesi is the stressed (emphatic) form; si is the unstressed clitic.

Neutral: Ako si umorna, …
Emphatic/contrastive: Ako jesi umorna, … (if you really are tired / if indeed you are tired)

Do I need the comma? What if I switch the order?

Yes, when the if-clause comes first you write a comma:

Ako si umorna, možeš biti kod kuće. If you reverse the order, a comma is usually not used:
Možeš biti kod kuće ako si umorna.

Can I say kad(a) instead of ako? What’s the nuance?

ako = “if” (a condition that may or may not be true).
kad/kada = “when/whenever” (habitual or time-based). So:
Ako si umorna, možeš ostati kod kuće. = If you’re tired (on any given occasion), you may stay home.
Kad si umorna, ostaješ kod kuće. = When(ever) you’re tired, you (tend to) stay home. (general habit)

How do I say it politely (using Vi) or to a group?

Use 2nd person plural for both polite singular and real plural:

Polite to one person (gender-neutral, widely used): Ako ste umorni, možete biti/ostati kod kuće.
To a group of women: Ako ste umorne, možete biti/ostati kod kuće. Note: In practice, with polite Vi to a woman you will also hear Ako ste umorne. Usage varies. A neat workaround is to rephrase: Ako se osjećate umorno, možete ostati kod kuće.

How would I talk about a future condition?

Two common options:

Present for future time (very common): Ako si sutra umorna, možeš ostati kod kuće.
Future with “budeš”: Ako budeš umorna, možeš ostati kod kuće. Avoid Ako ćeš biti umorna in standard style; budeš or the present is preferred after ako.

How do I express a past or a hypothetical condition?

Past real condition: Ako si bila umorna, mogla si ostati kod kuće. (If you were tired, you could have stayed home.)
Present hypothetical: Da si umorna, mogla bi ostati kod kuće. You’ll also hear Ako bi bila umorna, mogla bi … in everyday speech; many speakers use it, though some style guides prefer the da-construction.

Does možeš mean “can” (ability) or “may” (permission)? Could I use smiješ?

možeš can mean either “can” or “may,” and in contexts like this it’s permission. smiješ specifically means “may/is allowed to,” so:

Ako si umorna, smiješ ostati kod kuće. (explicit permission) Both are natural; možeš is more neutral and very common.

Can I just say Možeš kući?

That usually implies motion (“You can go home”). If that’s what you mean, say Možeš ići kući. To express being/staying at home, use:

možeš biti kod kuće (be at home)
možeš ostati kod kuće (stay at home)

Are there colloquial alternatives to kod kuće?

Yes:

doma is very common: Ako si umorna, možeš ostati doma.
Some regions say kući for “at home” (e.g., Jesam kući), but standard language prefers kod kuće for location and kući for direction (Idem kući).

Any spelling/pronunciation tips for this sentence?

možeš has ž like the “s” in “measure.”
kuće has ć, a softer “ch” than č. There’s no simple rule for č/ć—learn the word forms: kuća → kuće.
Stress is typically on the first syllable of umorna and možeš in standard pronunciation.