Mielőtt feladom a levelet, ráírom a címet a borítékra.

Mielőtt means before and introduces a subordinate clause.

So in Mielőtt feladom a levelet, ..., the first part means before I mail/post the letter. Hungarian uses a full clause here, with a normal finite verb, just like English does in before I mail the letter.

The clause can also come after the main clause: Ráírom a címet a borítékra, mielőtt feladom a levelet.

Because a levelet is a definite direct object, Hungarian uses the definite conjugation.

• feladok = I post/mail something indefinite
• feladom = I post/mail it / the ... something definite

Compare:

• Feladok egy levelet. = I’m mailing a letter.
• Feladom a levelet. = I’m mailing the letter.

This is a very common Hungarian pattern: the form of the verb changes depending on whether the object is definite.

The -t marks the accusative case, which usually marks the direct object.

Here the direct objects are:

• a levelet = the letter
• a címet = the address

So:

• feladom a levelet = I mail the letter
• ráírom a címet = I write the address onto it

The exact form is not always just a simple -t added mechanically. Hungarian often inserts a vowel or slightly changes the stem:

• levél → levelet
• cím → címet

In this sentence, felad means to mail / post / send off.

The prefix fel- often has a literal meaning like up, but in many verbs the whole prefixed verb has an idiomatic meaning that you should learn as one unit. So here it is best to learn:

• felad egy levelet = post/mail a letter

You may also meet felad with other meanings in other contexts, such as give up or hand in/send in, depending on the object.

Ráírom breaks down like this:

• rá- = onto it / on top of it
• ír = write
• -om = I with a definite object

So ráírom means something like I write it onto it or more naturally I write it on.

In the full sentence: ráírom a címet a borítékra = I write the address onto the envelope.

The prefix rá- matches the idea of putting writing onto a surface.

Because -ra / -re means onto a surface, or to a surface.

That fits the idea here: you are writing the address onto the envelope.

Compare:

• a borítékra = onto the envelope
• a borítékon = on the envelope
• a borítékba = into the envelope

Hungarian often treats writing something on a surface as movement onto that surface, so -ra is natural here.

Because all three nouns are understood as specific/definite in the situation:

• a levelet = the letter
• a címet = the address
• a borítékra = onto the envelope

Hungarian uses definite articles in many of the same situations as English, though not always identically. In this sentence, the speaker is talking about a particular letter, a particular address, and the envelope connected with that letter.

Because Hungarian usually leaves subject pronouns out when the verb ending already shows the subject clearly.

• feladom already means I mail/post
• ráírom already means I write it on

So én is unnecessary unless you want emphasis or contrast:

• Én adom fel a levelet. = I’m the one mailing the letter.
• Én írom rá a címet. = I’m the one writing the address on it.

Yes. Hungarian word order is flexible, and changes in word order often change focus or emphasis, not just style.

The given version is fairly neutral: Mielőtt feladom a levelet, ráírom a címet a borítékra.

But you could say:

• Mielőtt feladom a levelet, a borítékra írom rá a címet.

  • This can put more attention on the envelope.

• A címet írom rá a borítékra, mielőtt feladom a levelet.

  • This can emphasize the address.

So Hungarian word order is not random, but it is more information-structure-based than English word order.

No. In a neutral positive statement, they usually stay attached:

• feladom
• ráírom

But they can separate in certain structures, especially with focus or negation.

For example:

• Nem adom fel a levelet. = I’m not mailing the letter.
• A borítékra írom rá a címet. = It’s onto the envelope that I write the address.

So it is useful to think of felad and ráír as prefixed verbs, while also knowing that the prefix may move away from the verb in some sentence patterns.

Because Mielőtt feladom a levelet is a subordinate clause, and Hungarian separates subordinate clauses from the main clause with a comma.

So: Mielőtt feladom a levelet, ráírom a címet a borítékra.

This is standard Hungarian punctuation.

Yes, Hungarian often uses the present tense where English might also think of a future or near-future action, as long as the time relationship is clear from context.

So this sentence can work as:

• a habitual/general statement
• or a planned next action in context

Hungarian does not need a special future form here. The sequence is already clear from mielőtt.

A címet simply means the address as a direct object.

A címét would mean his/her/its address or the address of it, because -é- / -ja/-je-type possessive marking would be involved.

In this sentence, the address is just treated as a definite noun: ráírom a címet a borítékra = I write the address onto the envelope.

So címet is exactly what you want here.