Danas imam temperaturu.

• danas = today
• imam = I have
• temperaturu = a temperature / a fever (direct object form of temperatura)

So the sentence structure is literally Today I have a temperature.

In Serbian, the verb ending often already shows who the subject is.

• imam = I have
• imaš = you have
• ima = he/she/it has

Because -m in imam already means I, the pronoun ja is usually left out unless you want emphasis.

• (Ja) danas imam temperaturu. = I have a fever today.

Because temperaturu is in the accusative case.

The verb imati (to have) takes a direct object, and direct objects are usually in the accusative.

• nominative: temperatura
• accusative: temperaturu

So:

• Temperatura je visoka. = The temperature is high.
  Here temperatura is the subject, so it stays in the nominative.
• Imam temperaturu. = I have a fever.
  Here it is the object, so it becomes temperaturu.

Yes. In everyday Serbian, imam temperaturu commonly means I have a fever.

Literally, temperatura means temperature, but in health-related context it very often means elevated body temperature / fever.

You may also hear:

• Imam povišenu temperaturu. = I have an elevated temperature.
• Imam visoku temperaturu. = I have a high fever.

Serbian often expresses this idea with imati (to have), just like English can say I have a fever.

So imam temperaturu is the normal, natural way to say it.

Other Serbian options exist, but they are different in tone or meaning:

• Bolestan sam. = I am sick.
  More general.
• Imam groznicu. = I have a fever.
  Possible, but imam temperaturu is very common in everyday speech.

Yes. Serbian word order is more flexible than English.

• Danas imam temperaturu. = neutral, with today emphasized first
• Imam temperaturu danas. = also possible
• Ja danas imam temperaturu. = emphasizes I
• Temperaturu imam danas. = possible, but more marked or contrastive

The most natural neutral version here is Danas imam temperaturu or simply Imam temperaturu.

No. Danas just adds the time meaning today.

• Imam temperaturu. = I have a fever.
• Danas imam temperaturu. = I have a fever today.

If the time is already clear from context, Serbian often leaves it out.

Because Serbian has no articles.

English says:

• a fever
• the temperature

Serbian does not have separate words for a/an/the. The meaning is understood from context.

So:

• Imam temperaturu. can naturally mean I have a fever.

A simple pronunciation guide is:

DAH-nahs EE-mahm tehm-peh-rah-TOO-roo

Very roughly:

• danas = DAH-nahs
• imam = EE-mahm
• temperaturu = tehm-peh-rah-TOO-roo

A few helpful notes:

• j in Serbian sounds like English y
• vowels are usually clear and consistent
• Serbian spelling is quite phonetic, so words are usually pronounced much as they are written

Yes, absolutely. Imam temperaturu is very natural.

A few common real-life variants are:

• Imam temperaturu.
• Danas imam temperaturu.
• Mislim da imam temperaturu. = I think I have a fever.
• Imam visoku temperaturu. = I have a high fever.

So this is a very useful everyday sentence.