الباص متاخر كتير اليوم.

In Levantine Arabic, as in Arabic generally, the present-tense to be is usually omitted.

So:

الباص متاخر كتير اليوم
literally looks like: the-bus late very today

But it naturally means: The bus is very late today.

This is normal with simple present descriptions:

• أنا تعبان = I am tired
• الجو حلو = The weather is nice

If you want past or future, then Arabic usually does use a word:

• كان الباص متأخر = The bus was late
• رح يكون الباص متأخر = The bus will be late

باص means bus. It is a common borrowed word in Levantine.

The ال at the beginning is the definite article, meaning the.

So:

• باص = a bus / bus
• الباص = the bus

In Levantine pronunciation, ال is often pronounced il-, so الباص is roughly il-baas.

Yes—if you write it more carefully, especially in Standard Arabic spelling, it is usually متأخر.

In casual writing, texting, or dialect writing, people often simplify the spelling and leave out the hamza, so متاخر is very common.

Both refer to the same word here: late.

So:

• متأخر = more standard spelling
• متاخر = very common informal spelling

A learner should recognize both.

متاخر / متأخر means late.

It is an adjective describing الباص.

Because الباص is treated as masculine singular, the adjective also appears in the masculine singular form:

• الباص متأخر = The bus is late

If the noun were feminine, the adjective would usually change:

• الحافلة متأخرة = The bus is late
  using حافلة, a more formal word for bus

كتير means a lot / very / much, depending on context.

After an adjective, it often works like very:

• متأخر كتير = very late
• حلو كتير = very nice
• صعب كتير = very difficult

So in this sentence, كتير is intensifying متاخر.

Its position after the adjective is normal in Levantine:

• متأخر كتير = very late

This may feel backwards to an English speaker, but it is the natural order here.

Basically yes.

كثير is the Standard Arabic form.
كتير is the common Levantine pronunciation/spelling.

Compare:

• Standard Arabic: كثير
• Levantine: كتير

So:

• متأخر كثيرًا = more formal / Standard Arabic style
• متأخر كتير = natural Levantine speech

Because اليوم is just the normal Arabic word for today, and it includes the definite article historically/formally.

You do not need to think of it as literally the day in this sentence. As a whole, اليوم simply means today.

This is very common and natural:

• اليوم = today
• بكرا = tomorrow
• مبارح = yesterday

So the ال in اليوم is just part of the normal word learners memorize.

Time expressions like اليوم are fairly flexible in Arabic.

The version you have:

• الباص متاخر كتير اليوم

is completely natural and means The bus is very late today.

You can also hear:

• اليوم الباص متاخر كتير

This puts more emphasis on today, as if contrasting it with other days.

So the end position is natural, but not the only possible one.

It is clearly colloquial, and it fits Levantine well.

Why:

• الباص is a common everyday spoken word
• كتير is strongly colloquial/Levantine
• متاخر without hamza is typical informal writing

A more Standard Arabic version might be:

• الحافلة متأخرة جدًا اليوم or
• الباص متأخر جدًا اليوم

So this sentence is the kind of thing you would expect in everyday speech or informal text, not in very formal written Arabic.

Arabic adjectives agree with the noun they describe.

Here, الباص is treated as masculine singular, so the adjective is masculine singular too:

• الباص متأخر

If the noun were feminine, you would use the feminine adjective:

• الحافلة متأخرة كتير اليوم

That final ـة on متأخرة marks the feminine form.

A rough pronunciation would be:

il-baas mta'akhkher ktiir il-yoom

A few helpful notes:

• الباص → il-baas
• متأخر often sounds something like mta'akhkher in Levantine
• كتير → ktiir
• اليوم → il-yoom

Regional pronunciation varies, so do not worry if you hear slightly different vowels or stress patterns. The important thing is recognizing the words in connected speech.

You might be understood, but متأخر كتير is the more natural Levantine order.

With adjectives, كتير usually comes after the adjective:

• متأخر كتير
• حلو كتير
• غالي كتير

So for a learner, the safest natural version is:

الباص متاخر كتير اليوم