A tömegközlekedés ma ingyenes.

Hungarian often leaves out the verb van (to be) in the present tense, third person when the predicate is a noun or adjective.

So:

• A tömegközlekedés ma ingyenes. = Public transportation is free today.

Literally, Hungarian says something like:

• The public transportation today free.

This is completely normal Hungarian.

You would use van if:

• the tense changes: A tömegközlekedés ma ingyenes volt. = Public transportation was free today.
• the person changes: Ingyenes vagyok = I am free
• you want to express existence or location in certain contexts

But in a simple present-tense sentence like this, no is is needed.

A is the definite article, meaning the.

So:

• a tömegközlekedés = the public transportation / public transport

Hungarian has two indefinite/definite article forms:

• a before most consonant sounds
• az before vowel sounds

Examples:

• a ház = the house
• az autó = the car

In this sentence, tömegközlekedés begins with a consonant sound, so it takes a.

Tömegközlekedés means public transportation or public transport.

It is a compound word:

• tömeg = mass, crowd
• közlekedés = transport, traffic, transportation, getting around

So the literal idea is something like mass transportation.

This is a very common feature of Hungarian: long compound words are normal and very productive.

Ma means today.

Hungarian word order is flexible, and position often reflects focus or emphasis, not just grammar.

In:

• A tömegközlekedés ma ingyenes.

the structure feels neutral and natural:
Public transportation is free today.

Other orders are also possible, with slightly different emphasis:

• Ma ingyenes a tömegközlekedés. = Today, public transportation is free.
  Stronger focus on today
• Ingyenes ma a tömegközlekedés. = more marked, emphasizing free

So ma is in the middle because Hungarian often places time expressions there naturally, but it is not the only possible position.

Yes. Ma a tömegközlekedés ingyenes is also correct.

These versions are all possible:

• A tömegközlekedés ma ingyenes.
• Ma a tömegközlekedés ingyenes.
• Ma ingyenes a tömegközlekedés.

They all mean roughly the same thing, but the emphasis changes a bit:

• A tömegközlekedés ma ingyenes. = neutral statement
• Ma a tömegközlekedés ingyenes. = today is a bit more foregrounded
• Ma ingyenes a tömegközlekedés. = stronger focus on today or on the fact that it is free

So yes, word order can change, but not randomly: it usually changes what sounds most important.

This is a very useful distinction.

• ingyen = for free, free of charge
  This behaves more like an adverb.
• ingyenes = free, complimentary
  This behaves like an adjective.

In your sentence:

• A tömegközlekedés ma ingyenes.
  Public transportation is free today.

You could also hear:

• Ma ingyen lehet utazni.
  Today you can travel for free.

Compare:

• A belépés ingyenes. = Admission is free.
• Ingyen mehetek be? = Can I go in for free?

So here ingyenes is used because it describes the noun tömegközlekedés.

Because it is the subject of the sentence, and the basic subject form in Hungarian is the nominative, which usually has no ending.

So:

• tömegközlekedés = subject form

Hungarian adds endings mainly for other grammatical roles, for example:

• tömegközlekedéssel = by public transport
• tömegközlekedést = public transport as a direct object
• tömegközlekedésre = onto / for public transport, depending on context

But in your sentence, it is simply the thing being talked about, so no extra ending is needed.

It is singular in form, but like English public transportation/public transport, it refers to a whole system collectively.

So even though many buses, trams, and trains may be involved, Hungarian treats tömegközlekedés as a singular mass/collective concept.

That is why the sentence is not plural.

A rough pronunciation guide is:

• tö-meg-köz-le-ke-désh

A few important sound notes:

• ö is like the vowel in German schön or French peu; English does not have an exact match
• é is a long ay-like sound, but pure and steady
• s in Hungarian is pronounced like English sh
• sz is the normal English s

So the end -dés sounds roughly like daysh, but with a pure Hungarian vowel.

If you want to break the word into parts:

• tömeg
• közlekedés

That often makes it easier to say.

Yes, it is natural and idiomatic.

It sounds like something you might see:

• in an announcement
• on a sign
• in the news
• in a transit app
• on a holiday notice

For example, a city might announce free travel on a special day, and this sentence would be completely normal.

It is also slightly formal/informational in tone because tömegközlekedés is a general public-information word. In casual speech, people might sometimes refer more specifically to:

• a buszok
• a villamos
• a metró
• a közlekedés

But the given sentence itself is perfectly standard.

Usually, yes—that is the normal interpretation.

Because a tömegközlekedés refers to public transportation as a system, the sentence generally means that public transport in the relevant place is free today.

As always, the exact scope depends on context:

• in one city, it may mean that city’s transit system
• in a special announcement, it may refer to a particular network or service area

So the grammar gives the general meaning public transportation is free today, while the real-world context tells you exactly where and for whom.