Předprodej začíná dnes.

Předprodej means presale, advance sale, or ticket sales in advance, depending on context.

It is made from:

• před- = before / in advance
• prodej = sale

So the basic idea is sale before the main sale/event.

Because in Czech it is treated as a single compound noun.

Czech often combines elements like this into one word, especially when the first part works like a prefix:

• před-
  • prodej → předprodej

So even though an English speaker may want to think of it as pre-sale, Czech normally writes it as one word.

Here předprodej is:

• nominative singular
• masculine inanimate

It is in the nominative because it is the subject of the sentence — the thing that starts.

You can see the agreement in the verb:

• Předprodej začíná = The presale starts

The verb is singular because předprodej is singular.

Začíná is the 3rd person singular present tense form of začínat.

So:

• začínat = to start / to begin
• začíná = starts / is starting / begins

It matches the singular subject předprodej.

This is a very natural question, because Czech has aspect.

• začínat = imperfective
• začít = perfective

So:

• začíná = from začínat
• začne = from začít

In announcements or schedules, Czech often uses the imperfective present very naturally:

• Předprodej začíná dnes. = Presale starts today.

You may also hear Předprodej začne dnes, which is also possible, but it can sound a bit more like a single future point.
For a simple announcement, začíná dnes is very normal and idiomatic.

Because Czech does not have articles like a, an, and the.

So předprodej can mean:

• presale
• the presale

The exact meaning depends on context.

That is completely normal in Czech. Learners often want to insert something like the, but Czech simply does not do that.

Because dnes is an adverb meaning today.

It works on its own, just like English today:

• dnes = today

So:

• Předprodej začíná dnes. = Presale starts today.

No preposition is needed.

Yes. Czech word order is more flexible than English.

The neutral order here is:

• Předprodej začíná dnes.

But you could also say:

• Dnes začíná předprodej.

That version puts more emphasis on today.

So the words can move, but the emphasis changes.
English word order is more fixed; Czech word order often helps show what is new, important, or highlighted.

A rough learner-friendly guide is:

• Předprodej ≈ PRZHED-pro-day
• začíná ≈ za-CHEE-naa
• dnes ≈ dnyes

A few useful points:

• Stress in Czech is usually on the first syllable of each word.
• č is pronounced like ch in chair.
• í and á are long vowels.
• The hardest sound here is ř in před-. It is a special Czech sound with no exact English equivalent.

So if you are practicing, focus especially on:

• před-
• -čí-
• dnes

They are important for pronunciation.

In začíná:

• č = the ch sound as in chair
• í = long ee
• á = long aah

In předprodej:

• ě affects the pronunciation of the preceding consonant group; it is not just a simple plain e
• the spelling pře- is a very common Czech pattern

So the marks are not optional: they help tell you how the word is pronounced, and sometimes they distinguish different words.