Το πρωτάθλημα αρχίζει τον Σεπτέμβριο.

Το πρωτάθλημα means the championship.

Grammatically:

• το = the for a neuter singular noun
• πρωτάθλημα = a neuter singular noun meaning championship

In this sentence, το πρωτάθλημα is the subject, so it appears in the nominative case.

Αρχίζει is the 3rd person singular present tense of αρχίζω, which means to begin / to start.

So:

• αρχίζω = I begin / start
• αρχίζει = he/she/it begins, or it begins

Since το πρωτάθλημα is singular, the singular verb form αρχίζει is used.

Greek often uses the present tense for things that are scheduled or generally true, just like English can.

So Το πρωτάθλημα αρχίζει τον Σεπτέμβριο is very natural and means something like:

• The championship begins in September
• The championship starts in September

This is not strange in either language. It can describe a regular or scheduled event.

Because after a verb like begins, the phrase in September is a time expression, and in Greek months in this kind of expression usually appear in the accusative case.

So:

• ο Σεπτέμβριος = September as a subject or dictionary form
• τον Σεπτέμβριο = in September

The article changes too:

• ο → nominative masculine singular
• τον → accusative masculine singular

In Greek, you often do not need a preposition like in with expressions of time such as months.

English says:

• in September

Greek commonly says:

• τον Σεπτέμβριο

So the idea of in is built into the Greek time expression, especially through the accusative case.

Very often, yes, especially in standard expressions like:

• τον Σεπτέμβριο = in September
• τον Ιανουάριο = in January

So for learners, the safest pattern is:

• article + month in the accusative for in + month

That is the most useful and natural pattern to remember.

Because months are capitalized in Greek, just as they are in English.

So:

• Σεπτέμβριος
• Οκτώβριος
• Ιανουάριος

all begin with a capital letter.

Yes. Greek word order is more flexible than English.

The neutral, straightforward order here is:

• Το πρωτάθλημα αρχίζει τον Σεπτέμβριο.

But other orders are possible for emphasis, such as:

• Τον Σεπτέμβριο αρχίζει το πρωτάθλημα.

This might emphasize when it begins.

Even though word order can change, the original sentence is the most neutral and easy-to-learn version.

A rough pronunciation guide is:

• To pro-TA-thlee-ma ar-khi-ZEE ton sep-TEM-vree-o

A few useful notes:

• θ sounds like th in think
• χ here sounds like a harsher sound, somewhat like the h in huge for many English speakers, though not exactly
• the stress marks show which syllable is stressed:
  • πρωτάθλημα
  • αρχιζί
  • Σεπτέμβριο

It can mean both starts and begins.

So this sentence can be translated naturally as either:

• The championship starts in September
• The championship begins in September

In everyday use, there is no important difference here.

The dictionary form is πρωτάθλημα.

It is a neuter noun ending in -μα, which is a very common neuter noun pattern in Greek.

Examples of the same type include nouns like:

• όνομα = name
• πρόβλημα = problem

So it is useful to recognize -μα nouns as often being neuter.

Yes. That would also be correct.

• Το πρωτάθλημα αρχίζει τον Σεπτέμβριο = present tense, often used for scheduled events
• Το πρωτάθλημα θα αρχίσει τον Σεπτέμβριο = explicit future, The championship will begin in September

Both are natural. The version without θα sounds a little more like a scheduled or regular fact.