القطار متأخر، فأعيد الحجز.

In Arabic, the present tense often uses a nominal sentence with no written or spoken equivalent of is/am/are.

So:

• القطار متأخر
• literally: the train delayed
• natural English: the train is delayed

If you want past or future, Arabic usually adds a verb such as:

• كان القطار متأخرًا = the train was delayed
• سيكون القطار متأخرًا = the train will be delayed

So the missing is is completely normal here.

Because متأخر here is the predicate of the sentence, not an adjective directly attached to القطار.

Compare:

• القطار متأخر = the train is delayed
• القطار المتأخر = the delayed train

This is a very common distinction in Arabic:

• definite noun + indefinite word often gives a full sentence
• definite noun + definite adjective gives a noun phrase

So القطار متأخر is a complete statement, not just a noun phrase.

The فـ here means so, therefore, or and so.

It links the two parts like this:

• القطار متأخر = the train is delayed
• فأعيد الحجز = so I rebook / so I redo the booking

This فـ often shows result, consequence, or the next step in a sequence.

So the logic is:

The train is delayed, so I rebook.

أعيد is the first-person singular imperfect form of أعاد, which means to repeat, redo, or restore.

Here it means something like:

• I redo
• I repeat
• with الحجز: I rebook / I redo the reservation

With vowels, it is أُعيدُ.

A rough pronunciation is:

• u-ʿee-du

Important points:

• the initial أ is the imperfect prefix for I
• the verb is not pronounced aعيد
• in this sentence, it is best understood as I rebook / I am rebooking / I will rebook, depending on context

Arabic often expresses this idea more literally as redo the booking/reservation.

So:

• أعيد = I redo / repeat
• الحجز = the booking / reservation

Together:

• أعيد الحجز
• literally: I redo the booking
• natural English: I rebook

This is very normal. Languages often package actions differently. English uses one compact verb, while Arabic may use a verb plus a noun.

Because it usually refers to a specific, understood reservation.

So الحجز here is not just any booking in general; it is more like:

• the booking
• the reservation
• the one relevant in the situation

That is why the definite article ال sounds natural.

In English, we often translate more freely and simply say rebook, even though the Arabic structure is closer to redo the reservation.

Grammatically, أعيد is in the imperfect, and the Arabic imperfect can cover several meanings depending on context:

• I rebook
• I am rebooking
• I will rebook

In this sentence, English might naturally choose future because it sounds like the speaker’s response to the delay:

• The train is delayed, so I’ll rebook.

But the Arabic form itself does not explicitly mark future here.

If you want to make the future completely clear, you could say:

• فسأعيد الحجز = so I will rebook
• فسوف أعيد الحجز = so I will rebook

A fully vocalized version would be:

القطارُ متأخِّرٌ، فأُعيدُ الحجزَ.

Those endings show the grammar:

• القطارُ: nominative, because it is the topic/subject of the nominal sentence
• متأخِّرٌ: nominative, because it is the predicate
• أُعيدُ: imperfect verb in the indicative
• الحجزَ: accusative, because it is the direct object

In normal Arabic writing, these short vowels and case endings are usually omitted, so you normally see:

القطار متأخر، فأعيد الحجز.