يقارن صديقي الدين ونسبة الفائدة.

It is basically:

verb + subject + object(s)

• يقارن = compares / is comparing
• صديقي = my friend
• الدين ونسبة الفائدة = debt and the interest rate

So the sentence is in a normal Arabic verbal sentence pattern.

Because in Arabic, especially in Modern Standard Arabic, it is very common to start a sentence with the verb.

So:

• يقارن صديقي... = My friend compares...

is very normal.

You could also say:

• صديقي يقارن...

This is also correct, but it puts a little more focus on my friend.

يقارن is the present tense form of قارن.

More specifically, it is:

• 3rd person
• masculine
• singular

So it means:

• he compares
• he is comparing

Because the subject is صديقي and that means my friend in the masculine, the verb is masculine singular too.

Because it is made of:

• صديق = friend
• ـي = my

So:

• صديقي = my friend

This ـي is a attached possessive pronoun. Arabic often shows possession this way instead of using a separate word for my.

This is a very common learner question, because Arabic usually leaves out short vowels in normal writing.

So الدين can represent different words, including:

• الدِّين = religion
• الدَّيْن = debt

In this sentence, because it is paired with نسبة الفائدة and the context is financial, it is most likely:

• الدَّيْن = debt

So the sentence should probably be read with the debt meaning here.

Because the ال definite article changes its pronunciation before certain letters called sun letters.

The letter د is a sun letter, so:

• ال + دَين is pronounced ad-dayn
• not al-dayn

In writing, the ل is still there, but in pronunciation it assimilates to the د.

The same would happen with الدِّين = ad-dīn.

Because this is an iḍāfa construction, often called a possessive or genitive construction.

It is made of:

• نسبة = rate / percentage
• الفائدة = the interest

Together:

• نسبة الفائدة = the interest rate

In an iḍāfa:

1. the first noun usually does not take ال
2. the second noun determines definiteness

So even though نسبة has no ال, the whole phrase can still be definite because الفائدة is definite.

That is why نسبة الفائدة can mean the interest rate.

A fully vocalized version would be:

يُقارِنُ صَديقي الدَّيْنَ ونِسْبَةَ الفائِدَةِ

Here is why:

• يُقارِنُ ends in ـُ because it is the present-tense verb
• صديقي is the subject
• الدَّيْنَ is a direct object, so it is accusative
• نِسْبَةَ is also a direct object, so it is accusative
• الفائِدَةِ is the second term of the iḍāfa, so it is genitive

In normal Arabic writing, these short vowels are usually omitted.

It is understandable, but many learners are taught more explicit patterns with قارن.

Very common patterns are:

• يقارن بين X وY = compares between X and Y
• يقارن X بـ Y = compares X with Y

So many speakers or teachers might prefer something like:

• يقارن صديقي بين الدَّين ونسبة الفائدة
• يقارن صديقي الدَّين بنسبة الفائدة

Your sentence is still understandable, but these alternatives may sound more idiomatic in careful MSA.

It can mean either one.

The Arabic present tense often covers both:

• he compares
• he is comparing

The exact meaning depends on context.

So without more context, يقارن صديقي... could mean either:

• My friend compares...
• My friend is comparing...

Because الدين ونسبة الفائدة is just a coordinated noun phrase:

• الدين = debt
• و = and
• نسبة الفائدة = the interest rate

Arabic, like English, does not need to repeat the verb here. One verb can govern both nouns together.

So it works like:

• He compares debt and the interest rate