Az informatika fontos.

Az is the definite article, so it means the.

Hungarian has two forms of the definite article:

• a before a consonant sound
• az before a vowel sound

Since informatika starts with i, the sentence uses az:

• az informatika
• but a könyv = the book

It works a lot like English a/an, except here it means the, not a/an.

In Hungarian, the verb to be is often left out in the present tense, third person when the predicate is a noun or adjective.

So:

• Az informatika fontos. = Information technology is important.

Hungarian does not need a separate word for is here.

But in other situations, forms of to be do appear:

• Én fontos vagyok. = I am important.
• Az informatika fontos volt. = Information technology was important.

So the missing is is completely normal.

Not always exactly. Informatika is a broad Hungarian word that can refer to things like:

• IT
• computing
• computer science
• the school subject IT/computing

So the best English translation depends on context.

In Az informatika fontos, it could naturally mean something like:

• IT is important
• Computing is important
• Computer science is important

If this is from a school context, it may especially suggest the subject IT/computing.

Here fontos means important, and it stays in its basic form because the subject is singular.

A few useful points:

• Hungarian has no grammatical gender, so there is no masculine/feminine agreement.
• Adjectives do not change for gender the way they might in some other languages.
• In this sentence, informatika is singular, so fontos is singular too.

If the subject were plural, Hungarian would normally show that:

• A könyvek fontosak. = The books are important.

So in your sentence, fontos is exactly the form you would expect.

Yes, you could also say Fontos az informatika, but the nuance changes.

• Az informatika fontos. is the more neutral version.
• Fontos az informatika. puts more focus/emphasis on important.

A rough way to feel the difference is:

• Az informatika fontos. = As for IT, it is important.
• Fontos az informatika. = IT is important / What is important is IT

Hungarian word order is strongly connected to topic and focus, not just fixed subject-verb-object rules.

In normal Hungarian, Az informatika fontos sounds much more natural.

Hungarian often uses the definite article with general concepts, fields of study, and school subjects when talking about them as a known category:

• A matematika nehéz. = Math is difficult.
• Az informatika fontos.

Without the article, Informatika fontos would sound unusual in ordinary speech, and more like a heading, note, or a very marked style.

So for everyday standard Hungarian, keep az.

A simple learner-friendly guide is:

• az ≈ uz
• informatika ≈ IN-for-mah-ti-kaw
• fontos ≈ FON-tosh

A few important pronunciation points:

• Hungarian stress is usually on the first syllable of each word.
• The letter s in Hungarian sounds like English sh.
  • so fontos ends in -tosh
• English s is usually written sz in Hungarian.

So:

• fontos = fon-tosh
• szép = sape (with English s, not sh)

In this sentence, informatika is a noun.

It names a field or subject: IT / informatics / computing / computer science.

If you want an adjective meaning IT-related or computer-related, Hungarian often uses informatikai instead:

• informatika = IT / informatics
• informatikai rendszer = IT system
• informatikai cég = IT company

So in Az informatika fontos, the structure is:

• az informatika = the subject
• fontos = the predicate adjective

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

In Hungarian, school subjects and academic fields are normally written with a lowercase letter unless they start the sentence:

• informatika
• matematika
• történelem

In your sentence, only Az is capitalized because it is the first word of the sentence.

So:

• Az informatika fontos. is correct
• Az Informatika fontos. would usually be wrong unless Informatika were somehow part of a title or name