Ona danas nosi plavu suknju.

Yes. Croatian often does drop subject pronouns because the verb ending already shows who is doing the action.

• nosi = he/she/it wears / carries
• So Nosi plavu suknju. can already mean She is wearing a blue skirt.

Adding ona makes the subject more explicit. It can be used:

• for emphasis
• for contrast: Ona nosi plavu suknju, a on crne hlače.
• when you want to make it extra clear who she is

So Ona danas nosi plavu suknju. is correct, but Danas nosi plavu suknju. is also natural in the right context.

In this sentence, nosi means is wearing.

The verb nositi can have several related meanings, including:

• to wear clothes
• to carry
• sometimes more general senses like to bear

Here, because the object is plavu suknju (a blue skirt), the meaning is clearly wearing.

So:

• Ona nosi plavu suknju. = She is wearing a blue skirt.

Not:

• She is carrying a blue skirt, unless the context strongly suggested that

Because plavu suknju is in the accusative case, not the nominative.

• plava suknja = blue skirt as a dictionary/basic form
• plavu suknju = blue skirt as the direct object of the verb

In this sentence, the skirt is the thing she is wearing, so it is the direct object:

• Ona nosi što? → plavu suknju

That is why both words change:

• plava → plavu
• suknja → suknju

It is accusative singular feminine.

Croatian uses the accusative for a direct object, which is the thing directly affected by the action.

Here:

• subject: Ona = she
• verb: nosi = wears / is wearing
• direct object: plavu suknju = a blue skirt

So the structure is:

• She
  • wears
    • a blue skirt

Because a blue skirt is the direct object, Croatian puts it in the accusative.

Because in Croatian, adjectives must agree with the nouns they describe.

That means the adjective matches the noun in:

• gender
• number
• case

Here the noun is:

• suknja = feminine singular

And in the sentence it is in the accusative singular, so the adjective must also be feminine singular accusative.

That gives:

• plava suknja → nominative
• plavu suknju → accusative

So the adjective does not stay in one fixed form. It changes to match the noun.

Because suknja is a feminine noun, and feminine nouns ending in -a usually change to -u in the accusative singular.

So:

• suknja = nominative singular
• suknju = accusative singular

This is a very common pattern:

• knjiga → knjigu
• žena → ženu
• haljina → haljinu

So suknja → suknju follows a normal Croatian declension pattern.

For the same reason: the adjective has to match the noun in case.

The basic form is:

• plava suknja = blue skirt in nominative singular feminine

But when the noun becomes accusative:

• plava → plavu
• suknja → suknju

So:

• nominative feminine singular: plava
• accusative feminine singular: plavu

This agreement is a core part of Croatian grammar.

No, Croatian word order is more flexible than English word order.

The neutral order here is:

• Ona danas nosi plavu suknju.

But you could also hear:

• Danas ona nosi plavu suknju.
• Plavu suknju ona danas nosi.
• Ona nosi plavu suknju danas.
  though this may sound less neutral depending on context

Changing the order often changes:

• emphasis
• focus
• what sounds most natural in context

English depends heavily on word order for grammar. Croatian depends more on case endings, so the order can move around more freely.

Yes. Danas means today, and adverbs like this can often appear in different positions.

Possible placements include:

• Ona danas nosi plavu suknju.
• Danas ona nosi plavu suknju.
• Ona nosi danas plavu suknju.

These are all understandable, but they may differ slightly in emphasis.

The version you were given,

• Ona danas nosi plavu suknju. is very natural and neutral.

The infinitive is nositi.

Present tense forms are:

• ja nosim = I wear / am wearing
• ti nosiš = you wear
• on/ona/ono nosi = he/she/it wears
• mi nosimo = we wear
• vi nosite = you (plural/formal) wear
• oni/one/ona nose = they wear

So nosi is the 3rd person singular present form:

• he/she/it wears
• he/she/it is wearing

It means is wearing, not puts on.

This is an important difference.

• nositi = to wear, to have on regularly or at the moment
• obući / odjenuti = to put on, to get dressed in

So:

• Ona nosi plavu suknju. = She is wearing a blue skirt.
• If you wanted She is putting on a blue skirt, you would use a different verb.

This is similar to the English difference between:

• wear
• put on

A simple approximate pronunciation for an English speaker is:

• Ona ≈ OH-nah
• danas ≈ DAH-nahs
• nosi ≈ NO-see
• plavu ≈ PLAH-voo
• suknju ≈ roughly SOOK-nyoo

A few helpful notes:

• Croatian pronunciation is fairly phonetic
• j is pronounced like English y
• u is like oo in food
• nj is a single sound, like the ny in canyon

So suknju may feel tricky at first because of the knj cluster, but with practice it becomes easier.

Not exactly. The adjective is usually listed in a form that shows its gender pattern, often as:

• plav = masculine
• plava = feminine
• plavo = neuter

So plava is the feminine nominative singular form.

Because suknja is feminine, the adjective starts from the feminine form:

• plava suknja

Then in this sentence it changes to accusative:

• plavu suknju

So plava is not the only form of the adjective; it is just one form of plav.