A meglepetésbuli decemberben lesz.

A is the Hungarian definite article, equivalent to English the.

So A meglepetésbuli means the surprise party.

Hungarian has two forms of the definite article:

• a before most consonant sounds
• az before vowel sounds

Here, meglepetésbuli starts with m, so the correct form is a.

Yes, it is one word, and it is a compound noun.

It is made of:

• meglepetés = surprise
• buli = party

So meglepetésbuli literally means surprise-party.

Hungarian very often combines words into one compound where English would use two separate words.

Because Hungarian usually adds a case ending instead of using a separate preposition like in.

The ending -ban / -ben means in.

So:

• december = December
• decemberben = in December

This is very typical in Hungarian. Instead of a separate word for in, the language often adds the meaning directly to the noun.

This is because of vowel harmony, an important feature of Hungarian.

Hungarian suffixes often come in two forms:

• back-vowel form: -ban
• front-vowel form: -ben

December contains front vowels, so it takes -ben:

• decemberben

Compare:

• házban = in the house
• kertben = in the garden

English speakers often just have to get used to learning suffixes in matching pairs like this.

Lesz is the future form of van / lenni, the verb to be.

In this sentence, lesz means will be.

So the structure is basically:

• A meglepetésbuli = the surprise party
• decemberben = in December
• lesz = will be

Hungarian often expresses future with lesz, especially when the meaning is literally that something will be / will happen / will take place.

Not exactly.

• van = is
• lesz = will be

So:

• A buli decemberben van. = The party is in December.
• A buli decemberben lesz. = The party will be in December.

In real Hungarian, the present tense can sometimes also refer to the future, depending on context, but lesz makes the future meaning very clear.

Hungarian word order is more flexible than English word order.

In a neutral sentence like this, putting the verb at the end is completely natural:

• A meglepetésbuli decemberben lesz.

But Hungarian word order often changes to show focus or emphasis.

For example:

• Decemberben lesz a meglepetésbuli.
  This puts more emphasis on in December.

So the word order is not random, but it is less rigid than in English.

Because in Hungarian, the names of months are normally written with a lower-case letter.

So:

• január
• február
• március
• december

This is different from English, where month names are capitalized.

So decemberben is written correctly with a lower-case d.

Because month names usually do not need an article in this kind of expression.

So Hungarian simply says:

• decemberben = in December

There is no separate word corresponding to English the here.

This is normal with months, days, and many time expressions.

Yes, buli is very common, but it does sound a bit more informal or everyday than a more neutral word like parti in some contexts.

So meglepetésbuli is a very natural everyday way to say surprise party.

It does not sound strange, but it is not especially formal.

In Hungarian, sz is pronounced like English s in see.

So lesz sounds roughly like less.

This is important because Hungarian spelling is quite regular:

• sz = English s
• s = English sh

So:

• lesz = pronounced with an s sound, not a z sound at the end like English les might suggest

In Hungarian, the stress is almost always on the first syllable of each word.

So you get:

• A MEG-le-pe-tés-bu-li
• DE-cem-ber-ben
• LESZ

That fixed first-syllable stress is one of the most predictable things about Hungarian pronunciation, and it helps a lot once you get used to it.