A fiú sokat jegyzetel az órán, mert hamarosan vizsga lesz.

Hungarian has two forms of the definite article:

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

So:

• a fiú = the boy
• az órán = in/during the class

Both a and az simply mean the. The choice depends only on the sound that follows, not on gender or case.

Sokat means a lot in this sentence.

It comes from sok = many / much / a lot, and with verbs Hungarian very often uses the -t form:

• sokat olvas = reads a lot
• sokat beszél = talks a lot
• sokat jegyzetel = takes a lot of notes / takes notes a lot

So even though it looks like it has an object ending, here it functions adverbially: it tells you how much he is taking notes.

Jegyzetel means to take notes or to make notes.

It is more specific than ír, which just means to write.

So:

• ír = write
• jegyzetel = take notes

The word is related to jegyzet, which means note or notes. So the verb clearly suggests classroom or study-note writing, not just any kind of writing.

Yes, literally the ending is the kind of case that often corresponds to on, but with óra it is idiomatic.

• óra can mean hour, but also lesson / class period
• órán means in class or during the lesson

So az órán is the normal Hungarian way to say in class here.

This is a good example of how Hungarian case endings do not always match English prepositions word-for-word.

Hungarian word order is strongly connected to emphasis and information structure.

In a neutral sentence, a word like sokat often comes before the verb:

• A fiú sokat jegyzetel.

This sounds natural and unmarked.

If you move it after the verb:

• A fiú jegyzetel sokat.

that is not impossible, but it sounds more marked or stylistically different. A learner should treat sokat jegyzetel as the normal pattern.

Because mert introduces a subordinate clause meaning because.

Hungarian normally uses a comma before such clauses:

• ..., mert hamarosan vizsga lesz.

So the comma here is standard Hungarian punctuation.

Hamarosan means soon or before long.

It is very common when talking about something that will happen in the near future:

• Hamarosan indulunk. = We’re leaving soon.
• Hamarosan vizsga lesz. = There will be an exam soon.

Hamar can also relate to soon / early / quickly, depending on context, but hamarosan is the clearer, more standard word for soon in sentences like this one.

Hungarian often uses a bare noun after van or lesz when simply stating what exists or what event is coming.

So:

• vizsga lesz = there will be an exam

This is very natural Hungarian.

You may sometimes also hear egy vizsga lesz, but the version without the article is extremely common when the speaker is just stating the fact that an exam is coming.

Yes. Lesz is the form used for will be.

Hungarian does not use a future tense in the same way English does. Often it expresses future through context, time words, or special verb forms. With to be, lesz is the normal form for future meaning:

• Ma óra van. = There is class today.
• Holnap vizsga lesz. = There will be an exam tomorrow.

So in this sentence, hamarosan plus lesz clearly gives the future idea: an exam will be soon / there will be an exam soon.

Fiú is pronounced in two syllables, roughly FEE-oo.

A few useful points:

• the stress is on the first syllable: FI-ú
• the ú is long, so it is held a little longer than a short u
• Hungarian stress is very regular: it almost always falls on the first syllable of the word

So in this sentence, the words are stressed like this:

• A FI-ú
• SO-kat
• JEGY-ze-tel
• az Ó-rán
• MERt
• HA-ma-ro-san
• VIZS-ga
• LESZ

That regular first-syllable stress is very different from English and helps a lot with pronunciation.