A tömegközlekedés jó.

A is the Hungarian definite article, so it corresponds to the.

In Hungarian, the definite article is often used with general or abstract nouns in places where English may use no article at all. So A tömegközlekedés jó. is a natural way to say that public transportation, as a system or general concept, is good.

So even if the English translation is just Public transportation is good, Hungarian normally keeps a here.

This is one of the most common things English speakers notice.

In Hungarian, in the present tense, when the subject is third person and the predicate is a noun or an adjective, the verb to be is usually omitted.

So:

• A tömegközlekedés jó. = Public transportation is good.

There is no visible word for is, but the sentence is complete and perfectly normal.

However, in other tenses, or in some other sentence types, the verb does appear:

• A tömegközlekedés jó volt. = Public transportation was good.
• A tömegközlekedés jó lesz. = Public transportation will be good.

Yes. Hungarian very often forms long compound words, and tömegközlekedés is one of them.

It is built from:

• tömeg = mass, crowd
• közlekedés = transport, traffic, travel, transit

Together, tömegközlekedés means public transportation / public transit.

So for an English speaker, it may look long, but for Hungarian this kind of compound is very normal.

A simple approximation is:

• tömegközlekedés ≈ TÖ-meg-köz-le-ke-désh
• jó ≈ yoh with a long o

A few helpful points:

• Stress in Hungarian normally falls on the first syllable of each word.
• ö is a rounded front vowel, somewhat like German ö or French eu.
• é is a long vowel.
• The final s in közlekedés is pronounced like English sh.
• ó in jó is also long.

So the accents are not decoration; they show real pronunciation differences.

Hungarian word order is more flexible than English word order. It is strongly influenced by topic and focus, not just by fixed subject-verb-object patterns.

In A tömegközlekedés jó.:

• A tömegközlekedés is the topic: what we are talking about
• jó is the comment/predicate: what we are saying about it

That makes this a very natural neutral word order.

You can also hear:

• Jó a tömegközlekedés.

That is also grammatical, but it can sound a bit more emphatic or context-driven, depending on the situation.

Jó is an adjective meaning good.

In this sentence it is used as a predicate adjective, meaning it describes the subject:

• A tömegközlekedés jó. = Public transportation is good.

It is not an adverb here.

Also, in this sentence it stays in its basic singular form because the subject is singular. If the subject were plural, the predicate adjective could be plural too:

• A buszok jók. = The buses are good.

It is in the nominative case, which is the basic dictionary form.

Here it is the subject of the sentence, so it does not need any extra case ending.

That is why you see just:

• tömegközlekedés

and not a form with a suffix such as -ban, -nak, -t, and so on.

Yes, absolutely.

In Hungarian, accent marks are an essential part of spelling. They usually show a real difference in vowel quality or vowel length.

For example:

• ö is not the same as o
• é is not the same as e
• ó is not the same as o

So you should learn the word together with its accents:

• tömegközlekedés
• jó

Ignoring the accents can lead to wrong pronunciation, and sometimes even a different word.

In normal everyday Hungarian, that would not be the natural way to say it.

For this kind of general statement, A tömegközlekedés jó. is the standard form. Leaving out a would sound unusual, incomplete, or very nonstandard in ordinary speech.

So as a learner, it is best to keep the article here.

To make it negative, add nem before the adjective:

• A tömegközlekedés nem jó. = Public transportation is not good.

To put it in the past, use volt:

• A tömegközlekedés jó volt. = Public transportation was good.

You can combine both:

• A tömegközlekedés nem volt jó. = Public transportation was not good.

This is a useful pattern to remember, because the present tense has no visible is, but the past tense does use the verb.