A rozmaring a virágcserépben van.

Because a is the Hungarian definite article the.

So the sentence literally breaks down as:

• A rozmaring = the rosemary
• a virágcserépben = in the flowerpot
• van = is

Hungarian often uses the definite article in places where English also uses the. Here, both the rosemary and the flowerpot are treated as specific.

Also, Hungarian has two forms of the definite article:

• a before a consonant
• az before a vowel

So:

• a rozmaring
• a virágcserépben but
• az alma = the apple

-ben is the Hungarian ending meaning in.

So:

• virágcserép = flowerpot
• virágcserépben = in the flowerpot

This is called a case ending. Hungarian often expresses meanings like in, on, to, from, etc. by adding endings to nouns instead of using separate prepositions the way English does.

A few similar examples:

• házban = in the house
• dobozban = in the box
• kertben = in the garden

This is because of vowel harmony, a very important feature of Hungarian.

Hungarian suffixes often come in two versions:

• -ban / -ben = in
• -ba / -be = into
• -nak / -nek = to/for

The choice depends on the vowels in the word.

• Words with mostly back vowels usually take -ban
• Words with mostly front vowels usually take -ben

virágcserép contains front vowels in its final part, so it takes -ben:

• virágcserépben

Compare:

• házban = in the house
• kertben = in the garden

For learners, the best habit is to memorize nouns together with a few common suffix forms.

That is a very common and very good question.

Hungarian often does omit the 3rd-person present tense of to be (van) in sentences like:

• A rozmaring zöld. = The rosemary is green.
• Ő tanár. = He/She is a teacher.

But when you are talking about location, Hungarian normally keeps van:

• A rozmaring a virágcserépben van. = The rosemary is in the flowerpot.
• A könyv az asztalon van. = The book is on the table.

So in this sentence, van is needed because the sentence says where something is.

The sentence is:

• A rozmaring = topic / what we are talking about
• a virágcserépben = location
• van = is

So the structure is roughly:

The rosemary + in the flowerpot + is

This may feel unusual to an English speaker, because English normally says:

The rosemary is in the flowerpot.

Hungarian word order is more flexible than English word order, but it is not random. It often depends on topic, focus, and what information is new or emphasized.

The neutral version here is perfectly natural:

• A rozmaring a virágcserépben van.

Yes, but changing the word order usually changes the emphasis.

For example:

• A rozmaring a virágcserépben van.
  Neutral: we are talking about the rosemary and saying where it is.

• A virágcserépben van a rozmaring.
  This can sound like It is in the flowerpot that the rosemary is or The rosemary is in the flowerpot with more attention on the location or on identifying what is there.

Hungarian word order is strongly connected to information structure, so different orders can all be grammatical but not identical in tone.

Because Hungarian usually uses suffixes instead of prepositions for this kind of meaning.

English:

• in the flowerpot

Hungarian:

• a virágcserépben

The meaning in is built into the noun by the ending -ben.

This is very typical of Hungarian. Instead of learning only nouns, it helps to learn how they behave with endings:

• asztal = table

• asztalon = on the table

• doboz = box
• dobozban = in the box

It is a compound noun:

• virág = flower
• cserép = pot / flowerpot / clay pot

Together:

• virágcserép = flowerpot

Hungarian makes compound nouns very freely, much like English does.

Then the ending -ben is added:

• virágcserépben = in the flowerpot

Because it is a common noun, not a proper name.

In Hungarian, as in English, ordinary nouns like plant names are normally not capitalized unless they begin the sentence.

Here it appears at the beginning of the sentence, but the capital letter belongs to the article A, not to rozmaring.

So:

• A rozmaring...

If the word appeared later, it would stay lowercase:

• A virágcserépben van a rozmaring.

Yes. That would mean in a flowerpot instead of in the flowerpot.

Compare:

• A rozmaring a virágcserépben van. = The rosemary is in the flowerpot.
• A rozmaring egy virágcserépben van. = The rosemary is in a flowerpot.

So the difference is the same as in English:

• a = the
• egy = a/an (and also the number one in other contexts)

A rough English-friendly guide is:

vee-raag-che-reyp-ben

A few helpful points:

• v sounds like English v
• í / á / é are long vowels
• cs is like ch in church
• r is usually rolled or tapped
• e is short, é is longer

So:

• virág ≈ vee-raag
• cserép ≈ che-reyp
• ben ≈ ben

And the whole word:

• virágcserépben

Even if your pronunciation is not perfect at first, getting the cs and the long vowels reasonably clear will help a lot.

Primarily location: it tells you where the rosemary is.

That is why van appears here. In Hungarian, sentences with van can express both existence and location, depending on context.

Here it is clearly a location sentence:

• The rosemary is in the flowerpot.

A related existential-style sentence would be something like:

• Van rozmaring a virágcserépben. = There is rosemary in the flowerpot.

That sentence has a different structure and emphasis: it introduces the existence of rosemary there, rather than talking about a particular rosemary as the topic.

Very literally, it is:

• A = the
• rozmaring = rosemary
• a virágcserépben = in the flowerpot
• van = is

So: The rosemary in-the-flowerpot is.

That literal order is not natural English, but it helps show how Hungarian builds the sentence.