الرحيل اليوم.

Because Arabic can make a complete sentence without an explicit verb in the present tense.

This is called a nominal sentence. In a sentence like الرحيل اليوم, Arabic is essentially saying:

• The departure is today
• or Departure is today

The verb is is understood and does not need to be written.

So the structure is roughly:

• الرحيل = the departure / departure
• اليوم = today

Together: Departure is today.

الرحيل is a verbal noun (called a maṣdar in Arabic) from the verb رَحَلَ = to depart / leave.

A maṣdar often works like an English noun such as:

• departure
• leaving
• travel (depending on context)

So الرحيل does not mean he leaves or leave! It is a noun, not a finite verb.

The prefix الـ is the Arabic definite article, usually equivalent to the.

So:

• رحيل = departure / a departure
• الرحيل = the departure

In short phrases like this, Arabic often uses the definite form where English may sound more natural with either the departure or just departure.

This is very common in Arabic. The word اليوم literally looks like the day, but it is also the normal way to say today in many contexts.

So here اليوم functions as a time expression meaning:

• today
• or more literally, on this day

Even though الـ is present, you should usually understand اليوم simply as today.

Here اليوم is a time expression telling us when the departure is.

So the sentence breaks down like this:

• الرحيل = the topic / subject-like part
• اليوم = the time element, meaning today

In traditional grammar, اليوم is often treated as an adverbial accusative of time (ظرف زمان).

So it is answering the question:

• When is the departure?
• Today.

A fully vowelled version would typically be:

الرَّحِيلُ اليَوْمَ

This shows the case endings:

• الرَّحِيلُ = nominative, because it is the main noun of the sentence
• اليَوْمَ = accusative, because it functions as a time adverb (ظرف)

In normal unvowelled writing, these short endings are usually not written.

Yes. In الرحيل, the ل of الـ is assimilated because ر is a sun letter.

So الرحيل is pronounced approximately:

ar-raḥīl

not

al-raḥīl

But in اليوم, the ل is pronounced normally because ي is a moon letter:

al-yawm

So the whole phrase is approximately:

ar-raḥīl al-yawm

If full case endings are pronounced, it would be:

ar-raḥīlu al-yawma

It can be a complete sentence in Arabic, because Arabic does not need is in the present tense.

So الرحيل اليوم can stand on its own as:

• The departure is today
• Departure is today

At the same time, it could also appear as a short notice, schedule entry, or headline, where Arabic often prefers brief noun-based phrasing.

Yes, Arabic word order can sometimes change for emphasis.

The neutral version here is:

الرحيل اليوم

This naturally presents the departure first, then tells you when.

A different order, such as اليوم الرحيل, would sound marked or context-dependent, and would usually be chosen for emphasis rather than as the most basic form.

So for a learner, الرحيل اليوم is the normal form to focus on.

Yes. Like many Arabic verbal nouns, الرحيل can have a range of related meanings depending on context, such as:

• departure
• leaving
• setting off
• sometimes even migration or moving on

But in this short sentence, the simplest reading is just departure or leaving.