صديقي يشترك في باقة اقتصادية.

Here يشترك means subscribes or is subscribed to a plan/package.

The verb comes from اشترك and its basic idea is connected to sharing, joining, participating, or subscribing. The exact English translation depends on context:

• يشترك في مسابقة = he participates in a competition
• يشترك في خدمة = he subscribes to a service
• يشترك في باقة = he subscribes to a package/plan

So in this sentence, subscribes to is the most natural meaning.

It can do both.

In Arabic, the imperfect verb يشترك can mean:

• he is subscribing
• he subscribes
• he usually subscribes / is on

In this sentence, the most natural reading is habitual or general present: My friend subscribes to an economical package or My friend is on an economical plan.

صديقي is made of:

• صديق = friend
• ـي = my

So صديقي means my friend.

This ـي is a possessive suffix. Arabic often shows possession by attaching a pronoun directly to the noun.

Examples:

• كتابي = my book
• بيتي = my house
• صديقي = my friend

Yes. صديق is masculine, so صديقي means my male friend.

If you want to say my female friend, you would say:

• صديقتي

Then the full sentence would become:

• صديقتي تشترك في باقة اقتصادية.

Notice that the verb also changes from يشترك to تشترك because the subject is now feminine.

Because its subject, صديقي, is masculine singular.

Arabic verbs agree with the subject in gender and number. So:

• صديقي يشترك = my male friend subscribes
• صديقتي تشترك = my female friend subscribes
• صديقاي يشتركان = my two friends subscribe
• أصدقائي يشتركون = my friends subscribe

So يشترك is the correct form for he subscribes.

Because اشترك في is a common Arabic pattern meaning to participate in or to subscribe to something.

So:

• يشترك في باقة = subscribes to a package
• يشترك في برنامج = participates in a program
• يشترك في خدمة = subscribes to a service

This is a good example of how Arabic and English use different prepositions. English says subscribe to, but Arabic often uses في here.

A useful contrast:

• اشترك في الباقة = subscribed to the package
• اشترك مع صديقه = shared/joined with his friend

So في is for the thing joined or subscribed to, while مع is often for the person you join with.

In this sentence, باقة means package, bundle, or plan.

In modern usage, it is very common for phone plans, internet plans, TV packages, and similar services.

Literally, باقة can also mean something like bouquet, but in commercial and service contexts it often means package or bundle.

So باقة اقتصادية means something like:

• an economical package
• a budget plan
• a low-cost package

Because اقتصادية is an adjective describing باقة, and باقة is feminine.

In Arabic, adjectives must agree with the nouns they describe in:

• gender
• number
• definiteness
• case

Since باقة is:

• singular
• feminine
• indefinite

the adjective must also be:

• singular
• feminine
• indefinite

So:

• باقة اقتصادية = an economical package

If the noun were masculine, you would use اقتصادي instead.

Because the phrase is indefinite.

• باقة اقتصادية = an economical package
• الباقة الاقتصادية = the economical package

In Arabic, when the noun is indefinite, the adjective is also indefinite.

So:

• باقة اقتصادية = indefinite + indefinite
• الباقة الاقتصادية = definite + definite

This matching is very important in Arabic adjective phrases.

Arabic allows both patterns:

• صديقي يشترك في باقة اقتصادية
• يشترك صديقي في باقة اقتصادية

Both are grammatical.

The version starting with صديقي is more topic-focused, like As for my friend, he subscribes to an economical package. It is very natural when the speaker wants to begin with the person being talked about.

The verb-first version can sound a bit more event-focused.

So the sentence you have is completely normal and natural.

With full vowel marks, the sentence is:

صَديقي يَشْتَرِكُ في باقَةٍ اقْتِصادِيَّةٍ.

A few useful points:

• يَشْتَرِكُ ends with ـُ because it is an indicative imperfect verb
• في makes the following noun genitive
• so باقَةٍ has a genitive ending
• the adjective اقْتِصادِيَّةٍ matches it and is also genitive

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

You would say:

صديقي يشترك في الباقة الاقتصادية.

Here both the noun and the adjective become definite:

• الباقة = the package
• الاقتصادية = the economical one

So:

• باقة اقتصادية = an economical package
• الباقة الاقتصادية = the economical package

Yes, a few:

• ص in صديقي is an emphatic s, heavier than normal س
• ش in يشترك is sh
• ق in باقة is a deep q sound, not an English k
• اقتصادية has the cluster قتص near the beginning, which can feel dense at first

A helpful transliteration is:

ṣadīqī yashtariku fī bāqatin iqtiṣādiyyatin

You do not need to rely on transliteration, but it can help at the beginning.