A penész fekete.

No. Hungarian a here is the definite article, so it means the, not English a/an.

Hungarian has two forms of the definite article:

• a before a consonant
• az before a vowel

So:

• a penész = the mold
• but az alma = the apple

Depending on context, a penész can mean a specific mold you are talking about, or sometimes mold in a more general sense.

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 Hungarian says:

• A penész fekete.

Where English needs:

• The mold is black.

This omission is completely normal.

But the verb does appear in other cases, for example:

• A penész fekete volt. = The mold was black.
• A penész fekete lesz. = The mold will be black.
• Fekete vagyok. = I am black.

Fekete is an adjective meaning black.

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

So the structure is:

• A penész = the subject
• fekete = what is being said about the subject

Hungarian does not have grammatical gender, so there is no masculine/feminine/neuter agreement to worry about.

In this sentence, the subject is singular, so fekete stays in its basic form.

If the subject is plural, a predicate adjective is often plural too:

• A falak feketék. = The walls are black.

So there is no gender agreement, but number can matter in predicate position.

A rough English approximation is peh-nays.

More carefully:

• pe sounds like pe in pet
• né has a long é sound, somewhat like the vowel in say, but cleaner and without much glide
• sz sounds like English s

The stress in Hungarian is always on the first syllable, so:

• PE-nész

Because Hungarian spelling works differently from English.

Important rule:

• sz = English s
• s = English sh

So:

• penész ends with an s sound
• if it were written with just s, it would sound like sh

This is one of the most important Hungarian spelling conventions to learn early.

The accent mark shows that the vowel is longer and also slightly different in quality.

So:

• e and é are not the same vowel
• é is a long vowel

In penész, the é should be pronounced longer than a plain e.

Vowel length matters in Hungarian, so accent marks are important and should not be ignored.

Yes, that is possible.

• A penész fekete. is the most neutral word order.
• Fekete a penész. puts more emphasis on fekete.

So the second version can sound like:

• The mold is black with special stress on black, perhaps contrasting it with another color or expectation.

Hungarian word order is often influenced by focus and emphasis, not just grammar.

Yes, Hungarian could use a plural, but the singular is very natural here.

Penész often behaves like a material or mass noun in context, similar to how English can say mold without making it plural.

A plural form such as penészek is possible, but it would usually suggest:

• different kinds of mold, or
• separate instances being talked about individually

So A penész fekete. is a normal and natural way to say it.