موظف المحطة في مكتب خدمة الركاب.

Because Arabic normally omits the present-tense to be in nominal sentences.

So موظف المحطة في مكتب خدمة الركاب can mean The station employee is in the passenger service office without any separate word for is.

If you wanted the past, you would usually add كان: كان موظف المحطة في مكتب خدمة الركاب = The station employee was in the passenger service office.

It is a nominal sentence:

• موظف المحطة = the subject
• في مكتب خدمة الركاب = the predicate, specifically a prepositional phrase showing location

So the pattern is:

• [subject] + [where that subject is]

Yes. موظف المحطة is an idafa construction, often translated as the station employee or literally employee of the station.

In an idafa:

• the first noun usually does not take ال
• the second noun makes the whole phrase definite if it is definite

So:

• موظف = employee
• المحطة = the station

Together:

• موظف المحطة = the station employee

Even though موظف has no ال, the whole phrase is definite because المحطة is definite.

Because Arabic often uses chained idafa constructions where English might use of or a noun compound.

Here is the breakdown:

• خدمة الركاب = passenger service
  literally: service of the passengers
• مكتب خدمة الركاب = passenger service office
  literally: office of passenger service

This kind of noun chain is very common in Modern Standard Arabic.

For the same reason: مكتب خدمة الركاب is also an idafa.

In a normal idafa, the first noun does not take ال. So:

• مكتب = office
• خدمة الركاب = the passenger service

Together:

• مكتب خدمة الركاب = the passenger service office

So the phrase can be definite even though مكتب itself does not have ال.

Because في is a preposition, and prepositions in Arabic normally make the following noun genitive.

So in a fully vowelled version:

• في مكتبِ = in an/the office
• then خدمةِ is genitive because it is the second noun in an idafa with مكتب
• then الركابِ is genitive because it is the second noun in an idafa with خدمة

So the genitive keeps repeating through the noun chain.

A fully vowelled MSA version would be:

مُوَظَّفُ الْمَحَطَّةِ فِي مَكْتَبِ خِدْمَةِ الرُّكَّابِ

Why these endings?

• مُوَظَّفُ: nominative, because it is the subject
• الْمَحَطَّةِ: genitive, because it is the second noun in an idafa
• مَكْتَبِ: genitive, because it follows في
• خِدْمَةِ: genitive, because it is the second noun in an idafa with مكتب
• الرُّكَّابِ: genitive, because it is the second noun in an idafa with خدمة

This is the taa marbuta.

A useful rule:

• in pause, it often sounds like -a / -ah
• when grammar endings are pronounced, or when the word is in idafa, it is pronounced -t

So here:

• خدمة الركاب is pronounced with t in careful speech: khidmat ar-rukkāb or fully inflected khidmatu r-rukkābi
• المحطة in fully inflected reading is al-maḥaṭṭati
• in less formal paused pronunciation, learners may hear al-maḥaṭṭa

Because ر is a sun letter.

When ال comes before a sun letter, the l sound assimilates to the next consonant. So:

• written: الركاب
• pronounced: ar-rukkāb

The spelling stays the same, but the pronunciation changes.

Yes, in some contexts it could look like a label or fragment, especially since written Arabic often leaves out case endings.

But in normal prose, the most natural reading is as a complete nominal sentence:

• موظف المحطة = subject
• في مكتب خدمة الركاب = predicate

So it is most naturally understood as The station employee is in the passenger service office.

You would change موظف to the feminine موظفة:

موظفة المحطة في مكتب خدمة الركاب

Everything else stays the same.

In a fully vowelled version: مُوَظَّفَةُ الْمَحَطَّةِ فِي مَكْتَبِ خِدْمَةِ الرُّكَّابِ