Learn Hardcore Croatian: Kava je bolja od čaja danas.

It’s genitive singular. The preposition od requires the genitive, and in comparisons Croatian typically uses od + genitive after a comparative adjective. So:

čaj (nom.) → čaja (gen.)
Other examples: viši od brata, bolje od mene, različito od onoga.

Why is it bolja and not bolji or bolje?

Adjectives agree with the noun in gender and number. Kava is feminine singular, so the comparative form is bolja.

Masculine: čaj je bolji
Feminine: kava je bolja
Neuter: mlijeko je bolje

What does je do? Can I drop it?

Je is the 3rd person singular of “to be” (biti) in the present tense. In normal sentences it’s required: Kava je bolja…. Dropping it (e.g., Kava bolja…) is ungrammatical except in headlines, notes, or very telegraphic style.

Where can I put danas? Are all positions okay?

All of these are grammatical, with slightly different emphasis:

Danas je kava bolja od čaja.
Kava je danas bolja od čaja.
Kava je bolja od čaja danas. Avoid: Kava danas je bolja… because the clitic je should be in “second position” in the clause (very early in the sentence).

Can I use nego instead of od in this comparison?

Yes: Kava je bolja nego čaj danas. Both od + genitive and nego + nominative are acceptable here; od is more common with simple noun comparisons. Use nego when the second part is a clause or contains a verb:

Bolje je nego što misliš.
Also note contrast (not comparison): Ne kava, nego čaj.

Does the sentence mean “coffee is better than usual today”?

No, it compares coffee with tea within the time frame “today.” To say “better than usual”:

Kava je danas bolja nego inače.
Kava je danas bolja nego obično.

How do I turn it into a yes/no question?

Use Je li at the start:

Je li kava danas bolja od čaja? You’ll also hear Da li je kava danas bolja od čaja? regionally/colloquially. In careful standard Croatian, prefer Je li….

How do I negate it?

Change je to nije:

Kava danas nije bolja od čaja.

How do I say “much/a lot/far better”?

Add an intensifier before the comparative:

Kava je danas mnogo/puno/znatno bolja od čaja.
For “by far”: Kava je danas daleko bolja od čaja.

How do I say “the best” (superlative)?

Use the prefix naj-:

Kava je danas najbolja.
Within a group: Kava je danas najbolja od svih pića.

Pronunciation tips for the tricky letters?

č = “ch” in “church” (so čaja ≈ “CHAH-ya”)
j = “y” in “yes”
a = “a” in “father”
v = like English “v” Stress varies by dialect; the simple sound values above will make you clearly understood.

Do I need articles like “the” in Croatian?

No. Croatian has no articles. Kava and čaj can mean “coffee/the coffee” and “tea/the tea” depending on context.

How would the adjective change with different noun genders or number?

Masculine subject: Čaj je danas bolji od kave.
Neuter subject: Mlijeko je danas bolje od čaja.
Feminine plural: Kave su danas bolje od čajeva. (Genitive plural of čaj is čajeva.)

Is od always followed by genitive in comparisons?

Yes. With comparisons you use od + genitive:

viši od sestre, stariji od mene, važnije od toga.

Is there any regional variation for the word “coffee”?

Yes. Standard Croatian uses kava. In Serbian and Bosnian you’ll see kafa:

Kafa je bolja od čaja danas. All other grammar in the sentence stays the same (e.g., od čaja, danas).