Az uzsonna kész.

Both a and az mean the in Hungarian. Which one you use depends on the sound that follows:

• a before a consonant
• az before a vowel

Since uzsonna begins with the vowel u, the correct form is az uzsonna.

Examples:

• a kenyér = the bread
• az alma = the apple

In Hungarian, the verb to be is often omitted in the present tense when talking about the third person.

So English The snack is ready becomes simply:

• Az uzsonna kész.

This is completely normal Hungarian.

Compare:

• Én fáradt vagyok. = I am tired.
• Te fáradt vagy. = You are tired.
• Ő fáradt. = He/she is tired.

Notice that in the third person singular, there is no separate word for is.

Kész is an adjective meaning ready.

In Az uzsonna kész, it works like the predicate adjective in English The snack is ready.

Hungarian often uses this structure:

• [noun] + [adjective]

Examples:

• A vacsora kész. = Dinner is ready.
• A tea forró. = The tea is hot.
• A leves finom. = The soup is tasty.

That is a very natural Hungarian sentence pattern.

A neutral statement often looks like this:

• The + noun + adjective

So:

• Az uzsonna kész.

This is the plain, neutral way to say it.

Hungarian word order is flexible, though, and it can change emphasis. For example:

• Kész az uzsonna.

This also means The snack is ready, but it puts a bit more focus on ready, as if announcing the result.

Yes. Az uzsonna kész and Kész az uzsonna are both correct.

The difference is mainly emphasis:

• Az uzsonna kész. = neutral statement
• Kész az uzsonna. = more like The snack is ready now or The snack is done

Hungarian often uses word order to show what is being emphasized.

A simple approximate pronunciation is:

• awz OO-zhon-naw kays

A few helpful notes:

• a in az sounds more like o in British hot than English a in cat
• u in uzsonna is like oo
• zs is pronounced like the s in measure
• sz would be like English s, but there is no sz here
• é in kész is a long vowel, something like ay in say, but purer
• s by itself in Hungarian sounds like English sh, but again, there is no plain s sound here except inside uzsonna as part of zs

Stress in Hungarian normally falls on the first syllable of each word:

• AZ UZSonna KÉSZ

Uzsonna usually refers to a light meal or snack, often in the late afternoon. It is a specifically Hungarian meal-word, so depending on context it may be translated as:

• snack
• afternoon snack
• light meal

It is not exactly the same as dinner or supper. In many contexts, snack is the safest translation.

It is singular.

If you wanted the plural, it would be:

• uzsonnák = snacks

So:

• Az uzsonna kész. = The snack is ready.
• Az uzsonnák készek. = The snacks are ready.

Notice that kész also changes in the plural:

• singular: kész
• plural: készek

In Hungarian, predicate adjectives do not change for gender, because Hungarian has no grammatical gender like masculine or feminine.

So kész stays the same whether the subject is something like:

• a leves = the soup
• a vacsora = the dinner
• az uzsonna = the snack

It only changes for number when needed:

• Az uzsonna kész. = The snack is ready.
• Az uzsonnák készek. = The snacks are ready.

Not always, but in this sentence the definite article is natural because it refers to a specific snack or meal that both speaker and listener know about.

• Az uzsonna kész. = The snack is ready.

Without the article, Uzsonna kész, the sentence would sound unnatural in normal speech.

Hungarian uses the definite article a lot in these everyday situations, often similarly to English the.

Yes, very often. This is a very common Hungarian pattern.

Examples:

• Az ebéd kész. = Lunch is ready.
• A vacsora kész. = Dinner is ready.
• A kávé kész. = The coffee is ready.
• A tea kész. = The tea is ready.

So once you know Az uzsonna kész, you can reuse the same structure with many nouns.