Ovaj čaj je blaži od kave.

Because ovaj has to agree with čaj in gender, number, and case.

• čaj is masculine
• it is singular
• here it is in the nominative because it is the subject of the sentence

So the correct demonstrative form is ovaj = this for a masculine singular noun in the nominative.

Compare:

• ovaj čaj = this tea
• ova kava = this coffee
• ovo vino = this wine

In Croatian, nouns have grammatical gender, and čaj is a masculine noun.

A few clues:

• many masculine nouns end in a consonant, and čaj does
• the demonstrative ovaj shows masculine agreement
• adjectives with it also take masculine forms

So in this sentence:

• ovaj čaj
• blaži

both are in masculine singular to match čaj.

Blaži is the comparative form of the adjective blag.

• blag = mild, gentle, not strong
• blaži = milder

So the sentence is using a comparison:

• Ovaj čaj je blag. = This tea is mild.
• Ovaj čaj je blaži od kave. = This tea is milder than coffee.

That is just how this adjective forms its comparative in standard Croatian.

With some adjectives, the stem changes a little in the comparative. Here:

• blag → blaži

The g changes to ž before the comparative ending. This kind of sound change is common in Slavic languages.

So you should learn it as a set:

• blag = mild
• blaži = milder
• najblaži = mildest

Because after od in this kind of comparison, Croatian normally uses the genitive case.

The basic noun is:

• kava = coffee

But after od:

• od kave = than coffee / of coffee / from coffee, depending on context

So in this sentence:

• blaži od kave = milder than coffee

The form kave is the genitive singular of kava.

Not always. Od has several meanings depending on context, but in comparisons it often corresponds to than in English.

Examples:

• veći od mene = bigger than me
• stariji od brata = older than his/her brother
• blaži od kave = milder than coffee

In other contexts, od can also mean things like from or of.

Sometimes yes, but od + genitive is the most straightforward pattern for this sentence.

For adjective comparisons, Croatian commonly uses:

• blaži od kave
• jači od čaja
• bolji od toga

You may also see nego in some comparisons, especially in broader sentence structures, but for a simple noun comparison like this, od kave is the standard and natural choice.

Je is the 3rd person singular form of the verb biti = to be.

So:

• Ovaj čaj = this tea
• je = is
• blaži od kave = milder than coffee

Croatian usually needs this verb in normal present-tense sentences like this, just as English needs is.

Yes, Croatian word order is more flexible than English, although some versions sound more natural in certain contexts.

The neutral order is:

• Ovaj čaj je blaži od kave.

You could also say:

• Ovaj je čaj blaži od kave.

That version is also natural and may sound slightly more flowing in some contexts.

What usually stays the same is the grammatical relationship:

• ovaj still matches čaj
• blaži still describes čaj
• od kave still gives the comparison

The letter ž is pronounced like the s in measure or the g in genre in many English accents.

So blaži sounds approximately like:

• BLA-zhi

with the stress typically on the first syllable.

Also:

• č in čaj sounds like ch in church
• j in Croatian sounds like y in yes

So čaj sounds roughly like chai.

Usually yes in this kind of sentence, but the nuance is worth noticing.

Blag often means:

• mild in taste
• not strong
• gentle
• soft

So with tea or coffee, it suggests that the flavor, intensity, or strength is not as strong.

Depending on context, English mild is usually the best translation, but the exact nuance can shift a little.

Because adjectives in Croatian agree with the noun they describe.

Here the noun is:

• čaj = masculine singular nominative

So the adjective must also be:

• blaži = masculine singular nominative comparative

If the noun changed, the adjective form would change too. For example:

• Ova kava je blaža. = This coffee is milder.

Here kava is feminine, so the adjective becomes blaža.

It may be understood, but the more standard and natural form here is:

• Ovaj čaj je blaži od kave.

That is the pattern learners should focus on first:

• comparative + od + genitive

So for this sentence, od kave is the best choice to remember.

Yes. In Croatian, just like in English, a noun can refer to something in general without an article.

Since Croatian has no articles like a or the, context does the work.

So kava here means coffee in general, not necessarily one particular cup of coffee.

That is why the sentence can naturally mean:

• this tea is milder than coffee

rather than only:

• this tea is milder than the coffee

Context would decide that.