أب صديقي في العمل.

Because Arabic usually leaves out the present-tense to be in simple sentences like this.

So instead of saying X is Y, Arabic often just puts: subject + predicate

Here:

• أب صديقي = the subject
• في العمل = the predicate

This kind of sentence is called a nominal sentence.

If you wanted was or will be, then Arabic would normally use a verb:

• كان أبو صديقي في العمل = was at work
• سيكون أبو صديقي في العمل = will be at work

Because Arabic possession works in the opposite order from English.

Arabic says: the thing possessed + the possessor

So:

• أب صديقي literally follows the pattern father of my friend

In English, we usually say:

• my friend’s father or
• the father of my friend

In Arabic, the possessed noun comes first.

Arabic often expresses possession without a separate word for of. This structure is called iḍāfa (the construct phrase).

So:

• أب صديقي = father of my friend
• not father of of my friend
• and not a phrase with a separate of

In an iḍāfa, the relationship itself is shown just by putting the two nouns together in the right order.

Because the first noun in an iḍāfa normally does not take الـ.

So in a phrase like:

• أب صديقي

the first noun أب cannot normally be الأب if it is part of this possession structure.

Also, the first noun in an iḍāfa does not take tanwīn either.

The whole phrase can still be definite, though. It becomes definite because the second part is definite:

• صديقي = my friend, which is definite
• so أب صديقي is also definite

The -ي here is the attached pronoun meaning my.

So:

• صديق = friend
• صديقي = my friend

This attached pronoun makes the noun definite automatically. That is why you do not need الـ on صديقي.

So صديقي is not just friend. It is specifically my friend.

In careful formal Arabic, yes, very often you would expect أبو here.

The noun أب is one of the five nouns, which often show case in a special way when they are in an iḍāfa:

• أبو = nominative
• أبا = accusative
• أبي = genitive

If this phrase is the subject of the sentence, the fully formal form would usually be:

• أبو صديقي في العمل

So the version with أب is best understood as a simplified or less fully inflected written form. A learner should know that أبو صديقي is the more careful MSA version here.

It is a prepositional phrase functioning as the predicate.

Breakdown:

• في = in / at
• العمل = the work / work

Together, في العمل means something like at work.

So the sentence structure is:

• أب صديقي = subject
• في العمل = predicate

Arabic very often uses a prepositional phrase as the predicate of a nominal sentence.

In theory, context can create ambiguity, but in a simple sentence like this, the normal reading is that في العمل is the predicate: is at work.

So the default interpretation is:

• [my friend’s father] [is at work]

If someone wanted to make at work describe my friend more clearly, Arabic would usually use a more explicit structure.

So for a learner, the safest reading here is that في العمل completes the sentence, not that it modifies صديقي.

Because في العمل is a very natural way to say at work or at the workplace.

Using الـ here often sounds more idiomatic and specific:

• في العمل = at work

If you said في عمل, it would more likely suggest something like:

• in a job
• in work
• in some work/task

So في العمل is the normal choice for the everyday idea of being at work.

In a careful fully inflected reading, it would usually be:

أَبُو صَدِيقِي فِي العَمَلِ

A common transliteration is: ʾabū ṣadīqī fī l-ʿamali

A few useful notes:

• أبو is the careful nominative form here
• صديقي is pronounced ṣadīqī
• العملِ is genitive after في
• at the very end of a sentence, speakers often pause, so the final short vowel may not be heard clearly

That is why in ordinary unvocalized writing, learners often see a simpler-looking form, even though the fully grammatical reading is more detailed.