A barátom barátai ma a parkban sétálnak.

A is the definite article “the” in Hungarian (used before consonant sounds; Az is used before vowel sounds).

In A barátom barátai ma a parkban sétálnak, the first A is “the”, just like the a before parkban (a parkban = in the park).

Hungarian normally uses the definite article in front of:

• specific people or things already known from context
• specific locations (like a parkban – in the park)
• specific possessed nouns (A barátom barátai – my friend’s friends = the friends of my friend)

So here, A barátom barátai = The friends of my friend.

These are both based on barát (friend), but they show different possession and number:

• barátom = my friend
  
  • barát (friend) + -om (my) → my friend (singular)
• barátai = (his/her) friends
  
  • barát (friend) + -ai (plural possessed) → friends belonging to someone

Put together:

• A barátom barátai = my friend’s friends
  
  • literally: the friends of my friend

So:

• barátom: my friend
• barátai: his/her friends
• A barátom barátai: my friend’s friends

For my friends (plural) you use a different ending:

• barátom = my friend (one friend)
• barátaim = my friends (more than one friend)

Forms side by side:

• barátom – my friend
• barátaim – my friends
• A barátom barátai – my friend’s friends (the friends belonging to my friend)

So if you wanted to say My friends are walking in the park today, you’d say:

• A barátaim ma a parkban sétálnak.

Hungarian does not use a separate verb like am/is/are with ordinary verbs in the present tense.

The information that English puts into “are walking” is all inside sétálnak:

• sétál- = the verb stem to walk
• -nak = marks 3rd person plural (they)

So sétálnak means “they walk / they are walking”, depending on context.
Hungarian simply uses the present tense form of the verb without an extra “are”.

The -nak / -nek ending here is a verb ending that shows:

• person: 3rd person
• number: plural (they)
• tense: present tense
• conjugation type: indefinite (because there is no definite object, like them / it being walked)

Compare:

• Ő sétál. – He/She walks / is walking. (3rd person singular)
• Ők sétálnak. – They walk / are walking. (3rd person plural → -nak)

In A barátom barátai … sétálnak, the subject (A barátom barátai) is plural, so the verb must be plural too: sétálnak.

-ban / -ben is the inessive case ending, meaning “in / inside”.

• park = park
• parkban = in the park

General pattern:

• ház – house → házban – in the house
• város – city → városban – in the city
• iskola – school → iskolában – in the school

The article makes it a parkban = in the park (specific park).
Without the article, parkban would be more like in a park / in parks (in general), depending on context.

The choice between -ban and -ben is based on vowel harmony, not on the consonant:

• With back vowels (a, á, o, ó, u, ú): use -ban
• With front vowels (e, é, i, í, ö, ő, ü, ű): use -ben

The word park has a, a back vowel, so it takes -ban:

• park → parkban (in the park)
• kert (garden, has e) → kertben (in the garden)

You don’t always need an article before a place word, but you often do when you mean a specific place.

• a parkban – in the park (a particular park, known from context)
• parkban sétálnak – they walk in (a) park(s) / in parks (more general, depends on context)

Typically you use a / az:

• before a specific place: a parkban, az iskolában, a városban
• before a specific person/thing: a barátom, a könyv, az autó

No article is used with many time expressions (like ma = today, holnap = tomorrow), but locations usually do take an article when you’re talking about a particular, known one.

Yes. Both are possible, but the neutral/typical order in everyday speech for this simple sentence is:

• A barátom barátai ma a parkban sétálnak.
  Subject – time – place – verb

If you say:

• Ma a parkban sétálnak a barátom barátai.

you put a bit more emphasis on Ma a parkban (Today, in the park, they walk…), and the subject comes at the end.

You can also say:

• A barátom barátai a parkban ma sétálnak.

This is grammatically correct but sounds more marked, with a special emphasis (e.g. It’s today that they are walking in the park).

For a learner, it’s safest to stick to:

• [Subject] + ma + [place] + [verb]
  → A barátom barátai ma a parkban sétálnak.

Hungarian has one present tense, and context decides whether English uses:

• simple present (walk)
• present continuous (are walking)
• near future (are going to walk / will walk)

In A barátom barátai ma a parkban sétálnak:

• it could mean they are currently walking there today
• or it could also be used for a planned event today, like My friend’s friends are going to walk in the park today.

Hungarian often uses the present tense with a time word (ma, holnap, jövő héten) where English uses a future form:

• Holnap a parkban sétálnak. – They will walk / are going to walk in the park tomorrow.

To negate a verb in Hungarian, you put nem in front of the verb.

So:

• A barátom barátai ma a parkban sétálnak.
  → My friend’s friends are walking in the park today.

Negated:

• A barátom barátai ma a parkban nem sétálnak.
  → My friend’s friends are not walking in the park today.

The position before the verb is crucial:

• nem sétálnak = do not walk / are not walking
• Everything else in the sentence stays the same.