Learn Hardcore Croatian: Danas sam umornija nego jučer, ali mi je srce mirno i puna sam radosti. - Today I am more tired than yesterday, but my heart is calm and I am full of joy.

Danas sam umornija nego jučer. = Today I am more tired than yesterday.
Danas sam više umorna nego jučer. is understandable, but sounds less natural here; it’s used more for emphasis or with adjectives that don’t form a normal comparative.

Using umornija is the standard and most idiomatic choice.

Why is umornija feminine? What if the speaker is male?

Adjectives in Croatian agree in gender, number, and case with the noun (or pronoun) they describe.

Here, the understood subject is ja (I). The form umornija is feminine singular, so the speaker is understood to be a woman.

Female speaker: Danas sam umornija nego jučer.
Male speaker: Danas sam umorniji nego jučer.

Only the ending changes:

-a → positive feminine (umorna)
-ija → comparative feminine (umornija)
-i → comparative masculine (umorniji)

Why is the word nego used here and not od?

Both nego and od can translate as than, but they’re used a bit differently.

In comparisons with adjectives/adverbs in the comparative:

nego is preferred when you compare to another quality, clause, or adverb like “yesterday”:
- umornija nego jučer (more tired than yesterday)
- ljepše nego što sam očekivao (more beautiful than I expected)
od is common when you compare directly to a noun or pronoun:
- veći od brata (bigger than (my) brother)
- važniji od toga (more important than that)

Here jučer (yesterday) is like an adverbial time expression, so nego jučer is the natural choice.

What does mi mean in ali mi je srce mirno? Is it “we”?

Here mi is not “we”. It’s the dative clitic meaning “to me / my” in this structure.

mi can be:
- nominative plural: we → mi idemo (we are going)
- dative/locative singular clitic: to me → mi je srce mirno (my heart is calm / the heart to me is calm)

In ali mi je srce mirno, it functions as a kind of dative of possession:

literally: “but to me is the heart calm”
natural English: “but my heart is calm”

Why is the word order mi je srce mirno and not moje srce je mirno?

Both are grammatically correct, but they differ in style and emphasis:

ali mi je srce mirno
- very natural, conversational Croatian
- uses dative mi (to me) + srce as subject
- emphasizes the state as it relates to me: “but my heart is calm”
ali moje srce je mirno
- more literal: “but my heart is calm”
- uses possessive adjective moje
- feels a bit more explicit/formal or emphatic about “my heart” itself

In everyday speech, dative + noun (like mi je srce) is very common to express possession.

Why is the auxiliary sam in second position (Danas sam umornija) and not Danas umornija sam?

Croatian has a strong tendency to put short unstressed words (clitics), including the auxiliary sam, in the second position in the clause (the “second position clitic rule”).

So:

✔ Danas sam umornija nego jučer.
✖ Danas umornija sam nego jučer. (sounds wrong/very unnatural)

Rough rule: the first stress-bearing element (here Danas) comes first, and then clitics like sam, si, je, mi, ti follow, usually as a little “cluster” in second place.

In ali mi je srce mirno i puna sam radosti, what is the subject of puna sam radosti? Is it still srce?

No. In puna sam radosti, the subject is I (ja) again, not srce.

The sentence actually has two separate predicates:

(ja) sam umornija – I am more tired
(meni) je srce mirno – my heart is calm
(ja) sam puna radosti – I am full of joy

In the second part, the subject of je srce mirno is srce (heart).
In the third part, the subject of sam puna radosti is again the implicit “ja” (I).

That’s why puna is feminine, agreeing with ja (female speaker), not with srce (which is neuter).

Why is it puna sam radosti and not ja sam puna radosti or sam puna radosti ja?

All three are possible, but differ in naturalness and emphasis:

puna sam radosti
- very natural, neutral word order in speech
- puna is stressed, sam is a clitic in second position
- subject ja is understood
ja sam puna radosti
- more explicitly emphasizes “I”
- used if you want to contrast: Ja sam puna radosti, ali on nije.
sam puna radosti ja
- technically possible, but sounds poetic or very emphatic, not normal everyday speech

The version in the sentence, puna sam radosti, is idiomatic and flows well.

What case is radosti in puna sam radosti, and why is that case used?

Radosti is in the genitive singular of radost (joy).

Adjectives like pun / puna / puno (full) are typically followed by the genitive case to show what something is “full of”:

puna radosti – full of joy
pun nade – full of hope
puno ljudi – full of people

So:

puna sam radost – incorrect
puna sam radosti – correct (I am full of joy)

Could you say puna sam od radosti instead of puna sam radosti?

You might hear pun od + genitive colloquially in some expressions, but the standard, most natural form after pun/puna/puno is just the genitive, without od:

✔ puna sam radosti
✔ pun je ljubavi (he is full of love)
✖ puna sam od radosti (sounds non‑standard/colloquial or influenced by other languages)

So for correct standard Croatian, keep puna sam radosti.

Is jučer the same as juče? Which one is correct here?

In standard Croatian, the correct form is jučer (with č and ending -er).

jučer – standard Croatian (yesterday)
juče – standard Serbian, also commonly used in Bosnian, and heard in some spoken varieties

So, in Croatian:

✔ Danas sam umornija nego jučer.

Could the sentence be more explicit, like ali moje srce je mirno i ja sam puna radosti?

Yes, that’s grammatically correct:

Danas sam umornija nego jučer, ali moje srce je mirno i ja sam puna radosti.

This version:

spells out moje srce instead of using mi
adds ja explicitly

It sounds a bit more formal, explicit, or emphatic.
The original:

Danas sam umornija nego jučer, ali mi je srce mirno i puna sam radosti.

is more natural and flowing in everyday Croatian, using clitics (mi, sam) and omitting obvious pronouns.