A szkenner hasznos.

Here, a is the Hungarian definite article, so it corresponds to English the.

A useful thing to know is that Hungarian often uses a/az in places where English might or might not use the, depending on context. So A szkenner hasznos can be a normal sentence both for a specific scanner in context and for a more general statement, depending on the situation.

Also, this a is not pronounced like English a.

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

So:

• A szkenner hasznos. = The scanner is useful.

This is completely normal Hungarian.

But in other tenses, the verb appears:

• A szkenner hasznos volt. = The scanner was useful.
• A szkenner hasznos lesz. = The scanner will be useful.

So the missing is is not an omission in the casual sense. It is simply how Hungarian grammar works.

Hungarian has two forms of the definite article:

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

Since szkenner begins with the consonant sound sz, the correct article is a:

• a szkenner

If the next word began with a vowel, you would use az instead.

It is a real word used in Hungarian, but it is a loanword based on English scanner.

Hungarian spelling has adapted it to Hungarian sound patterns:

• English scanner
• Hungarian szkenner

A very important spelling point is that Hungarian sz is a single letter combination that represents the English s sound. So szkenner starts with an s sound, not a sh sound.

A rough English-friendly guide would be:

• a ≈ short o sound, like British lot
• szkenner ≈ SKEN-ner
• hasznos ≈ HOSS-nosh

A more careful breakdown:

• a = ɒ
• sz = English s
• e = eh
• hasznos:
  
  • sz = s
  • final s = sh

So hasznos sounds roughly like HOSS-nosh, not haz-nos.

Also, Hungarian normally stresses the first syllable of each word:

• A SZKEN-ner HASZ-nos

No, not in the way an English speaker might expect from some other European languages.

Hungarian does not have grammatical gender, so adjectives do not change for masculine, feminine, or neuter.

With a singular subject, the predicate adjective simply appears in its basic form:

• A szkenner hasznos.

So there is no gender agreement to worry about here.

One thing to note: if the subject is plural, the predicate adjective is usually plural too:

• A szkennerek hasznosak. = The scanners are useful.

But in the singular, hasznos stays unchanged.

Yes, you could also say Hasznos a szkenner, but the emphasis changes.

The neutral, basic order is:

• A szkenner hasznos.

This simply states the fact.

If you say:

• Hasznos a szkenner.

then hasznos gets more emphasis, something like:

• The scanner is useful
• Useful is what the scanner is
• or in context, The scanner is useful, actually

So the original sentence is the most neutral version.

Because hasznos is the predicate of the sentence, not an adjective directly attached to the noun inside a noun phrase.

Compare:

• A szkenner hasznos. = The scanner is useful.
  Here hasznos is the predicate adjective.

• A hasznos szkenner = the useful scanner
  Here hasznos directly modifies szkenner inside the noun phrase.

So after the noun, it means something like is useful. Before the noun, it means useful scanner.

You would make both the noun and the predicate adjective plural:

• A szkennerek hasznosak. = The scanners are useful.

Changes:

• szkenner → szkennerek
• hasznos → hasznosak

And just like in the singular present tense, there is still no separate word for are here.

Usually not if you want the same feel as the original sentence.

• a/az = the
• egy = a/an or one

So:

• A szkenner hasznos. = The scanner is useful or a general statement depending on context
• Egy szkenner hasznos. = A scanner is useful or One scanner is useful

The second sentence is possible, but it has a different meaning and feel. It sounds more indefinite and often more like a general statement about any single scanner.

So if your model sentence is A szkenner hasznos, you should keep a there.