A rejtvény nehéz.

In Hungarian, the verb to be is usually left out in the present tense, third person when you are linking a subject to a noun or adjective.

So:

• A rejtvény nehéz. = The puzzle is difficult.
• literally: The puzzle difficult.

This is completely normal in Hungarian.

But the verb appears in other persons:

• Nehéz vagyok. = I am difficult / I am hard
• Nehéz vagy. = You are difficult
• A rejtvény nehéz. = The puzzle is difficult

It also appears in the past or future:

• A rejtvény nehéz volt. = The puzzle was difficult.
• A rejtvény nehéz lesz. = The puzzle will be difficult.

A is the Hungarian definite article, meaning the.

So:

• a rejtvény = the puzzle

Hungarian has two forms of the definite article:

• a before consonant sounds
• az before vowel sounds

Examples:

• a rejtvény = the puzzle
• az alma = the apple

Since rejtvény begins with a consonant sound, you use a.

Because nehéz is not directly describing the noun inside the noun phrase here; it is the predicate adjective.

Compare:

• A rejtvény nehéz. = The puzzle is difficult.
• a nehéz rejtvény = the difficult puzzle

So:

• before the noun = attributive adjective: a nehéz rejtvény
• after the noun = predicate adjective: A rejtvény nehéz.

This is a very important difference in Hungarian.

A rough English-friendly guide:

• rejtvény ≈ RATE-vayny
• nehéz ≈ neh-HAYZ

A few useful pronunciation points:

• Stress is always on the first syllable in Hungarian.
  • REJT-vény
  • NE-héz
• é is a long vowel, pronounced roughly like ay in say, but cleaner and tenser.
• ny is like the ny in canyon.
• zs in Hungarian sounds like the s in measure.

So rejtvény can be tricky because of the consonant cluster, but the main thing is to keep the first-syllable stress.

Rejtvény is a noun. In this sentence it is the subject.

Structure of the sentence:

• A rejtvény = the subject, the puzzle
• nehéz = the predicate adjective, difficult

So the whole sentence means:

• The puzzle is difficult.

Also, rejtvény is in its basic dictionary form here, with no case ending added.

Not in this sentence.

Hungarian adjectives do not work like adjectives in some languages where they change for gender. Hungarian has no grammatical gender, so nehéz stays nehéz here.

With a singular subject:

• A rejtvény nehéz. = The puzzle is difficult.

With a plural subject, predicate adjectives are often plural:

• A rejtvények nehezek. = The puzzles are difficult.

So you may notice:

• singular: nehéz
• plural predicate: nehezek

But there is no masculine/feminine/neuter agreement to worry about.

Yes. Nehéz can mean both difficult/hard and heavy, depending on context.

Examples:

• A feladat nehéz. = The task is difficult.
• A táska nehéz. = The bag is heavy.

In A rejtvény nehéz, the natural meaning is The puzzle is difficult, not heavy, because that fits the context better.

Yes, but it means something different.

• A rejtvény nehéz. = The puzzle is difficult.
• Egy rejtvény nehéz. = A puzzle is difficult.

So the difference is the article:

• a = the
• egy = a/an or sometimes one

In many contexts, A rejtvény nehéz refers to a specific puzzle already known in the conversation.

A rejtvény nehéz is the neutral, straightforward word order.

Hungarian word order is flexible, but changing it usually changes the focus or emphasis.

Neutral statement:

• A rejtvény nehéz. = The puzzle is difficult.

If you move things around, you may add emphasis or a special contrast. For a beginner, it is best to learn this version as the normal one.

So yes, this sentence is standard and natural, but Hungarian word order is often about information structure, not just grammar.

The plural version is:

• A rejtvények nehezek. = The puzzles are difficult.

Changes:

• rejtvény → rejtvények = puzzle → puzzles
• nehéz → nehezek when used as a plural predicate adjective

So this is a useful pair to remember:

• A rejtvény nehéz.
• A rejtvények nehezek.

No. Hungarian does not have grammatical gender like many Indo-European languages do.

That means:

• nouns are not masculine/feminine/neuter
• adjectives do not change for gender
• articles do not change for gender

So A rejtvény nehéz is simpler in that sense than the equivalent sentence in many other European languages.