تهتم صديقتي بالطعام.

Because Arabic often uses verb-first word order.

So تهتم صديقتي بالطعام is a normal verbal sentence meaning literally something like:

is interested my friend in food

In natural English, of course, we say My friend is interested in food.

You could also say:

صديقتي تهتم بالطعام

That version is also correct, but it starts with the subject and can feel a bit more like My friend, she is interested in food.

Because the subject صديقتي means my female friend.

The base noun is:

• صديقة = a female friend

So the verb must agree with a feminine singular subject.
That is why Arabic uses:

• تهتم = she is interested / she cares

If the subject were a male friend, you would have:

• يهتم صديقي بالطعام = My male friend is interested in food

صديقتي breaks down like this:

• صديقة = female friend
• ـي = my

So:

• صديقتي = my female friend

A useful detail: when ـي is added, the final ة of صديقة changes to ت in writing and pronunciation:

• صديقة
• صديقتي

Because the final ة (taa marbuuTa) often sounds like -a when the word stands alone, but when a suffix is attached, it becomes a clear t sound.

So:

• صديقة = ṣadīqa
• صديقتي = ṣadīqatī

This is very common in Arabic. The same thing happens in words like:

• سيارة = car
• سيارتي = my car

Because the verb اهتمّ / يهتمّ normally uses the preposition بـ.

So Arabic says:

• يهتمّ بـ...
• literally: he/she is interested with / cares about ...

In natural English, we translate it as:

• to be interested in
• to care about

So:

• تهتم بالطعام = she is interested in food / she cares about food

This is just how the verb works in Arabic, much like English interested in uses in.

Because it comes after the preposition بـ.

In Arabic, a noun after a preposition is normally genitive, so:

• بِالطَّعَامِ

That final -i sound is the genitive ending.

So the structure is:

• بِ = with/about
• الطعامِ = the food / food

Arabic often uses the definite article ال in places where English does not.

So الطعام can mean:

• the food
• or more generally food

In this sentence, it most naturally means food in a general sense.

So even though the Arabic literally has the food, the English translation is usually just:

• My friend is interested in food

تهتم is the present-tense form of the verb اهتمّ.

A useful breakdown is:

• past: اهتمّت = she became interested / she cared
• present: تهتمّ = she is interested / she cares

This verb comes from the root:

• ه م م

In dictionaries, you will usually find it as:

• اهتمّ بـ = to be interested in, to care about

So in this sentence:

• تهتم = she is interested / she cares

It is written:

• بالطعام

But it is pronounced roughly:

• biṭ-ṭaʿām

This happens because ط is a sun letter, so the ل of ال is not pronounced separately.

So:

• بِ + الطعام
• written: بالطعام
• pronounced: biṭ-ṭaʿām

The ط sound is doubled in pronunciation.

Usually, in straightforward MSA learning contexts, صديقتي simply means my female friend.

It can sometimes mean girlfriend depending on context, but that is not automatically the default meaning.

So in a basic sentence like this, learners should normally understand it as:

• my female friend

Yes. صديقتي is the subject, so it is nominative in function.

However, with the ـي suffix (my), the usual case ending is not clearly visible the way it would be on a regular noun.

So grammatically it is still the subject of the sentence, but you do not see a separate obvious nominative ending on it.

That is why the clearly visible case marking in this sentence is easier to notice on:

• الطعامِ after the preposition بـ

Yes.

The verb اهتمّ بـ covers both ideas depending on context:

• to be interested in
• to care about
• to pay attention to

So تهتم صديقتي بالطعام could be understood as:

• My friend is interested in food
• My friend cares about food

If the context is hobbies or preferences, is interested in food is often the most natural translation.