في المجموعة تسعة مشاركين.

Arabic often puts the place phrase first when the meaning is something like there are ... in ....

So in في المجموعة تسعة مشاركين:

• في المجموعة = in the group
• تسعة مشاركين = nine participants

This order is very natural in Arabic for introducing what exists in a place. It is similar in meaning to:

• There are nine participants in the group.

Grammatically, في المجموعة is a fronted phrase, and تسعة مشاركين comes later as the main noun phrase.

Yes and no: the meaning of are is present, but Arabic does not normally use a present-tense verb to be in this kind of sentence.

So Arabic says:

• في المجموعة تسعة مشاركين

not something like:

• في المجموعة يكون تسعة مشاركين for ordinary there are meaning

This is normal in Arabic nominal sentences. English needs is/are here, but Arabic usually leaves it unspoken in the present tense.

Because في is a preposition meaning in, and nouns after prepositions go into the genitive case.

So:

• في = in
• المجموعةِ = the group, in the genitive

If fully vowelled, this part is:

• فِي الْمَجْمُوعَةِ

That final -i sound is the genitive ending.

This is one of the famous number rules in Arabic.

For the numbers 3-10, the number shows the opposite gender of the counted noun.

Here the counted noun is based on مشارك (participant), which is masculine. Because the noun is masculine, Arabic uses the feminine-looking form of the number:

• تسعة = nine, used with a masculine counted noun

If the counted noun were feminine, you would use:

• تسع

For example:

• في المجموعة تسع مشاركات = There are nine female participants / nine participants (feminine) in the group

Because after the numbers 3-10, the counted noun is normally plural in Arabic.

So Arabic says:

• تسعة مشاركين = nine participants

not:

• تسعة مشارك

This is different from some other number patterns in Arabic. For example, after 11-99 (in many cases), the counted noun is usually singular instead:

• أحد عشر مشاركًا = eleven participants

So this sentence follows the special rule for 3-10:

• number + plural counted noun

Because after numbers 3-10, the counted noun is not only plural, but also genitive.

The word مشاركون / مشاركين is a sound masculine plural, so its endings change by case:

• مشاركون = nominative
• مشاركين = accusative/genitive

Since the counted noun after تسعة is genitive, Arabic uses:

• مشاركين

So the fully analysed phrase is:

• تسعةُ مشاركينَ

Here:

• تسعةُ is nominative in the sentence as a whole
• مشاركينَ is genitive because it is the counted noun after 3-10

Because the phrase is indefinite: it means nine participants, not the nine participants.

In this sentence, the speaker is simply stating how many participants there are. That is why Arabic uses an indefinite counting phrase:

• تسعة مشاركين = nine participants

If you wanted to say the nine participants, Arabic would usually use a different structure, such as:

• المشاركون التسعة

So:

• تسعة مشاركين = nine participants
• المشاركون التسعة = the nine participants

A fully vowelled version is:

• فِي الْمَجْمُوعَةِ تِسْعَةُ مُشَارِكِينَ

A careful grammatical reading would be approximately:

• fī al-majmūʿati tisʿatu mushārikīna

Notes:

• الْمَجْمُوعَةِ is genitive after في
• تِسْعَةُ is nominative in the sentence
• مُشَارِكِينَ is genitive plural after the number

In everyday writing, these short vowels are usually not written.

Yes, that is also possible.

• هناك تسعة مشاركين في المجموعة = There are nine participants in the group

Using هناك can make the sentence feel closer to English there are. But the original sentence:

• في المجموعة تسعة مشاركين

is also completely natural and elegant Arabic.

Very roughly:

• في المجموعة تسعة مشاركين emphasizes the location first: In the group, there are nine participants
• هناك تسعة مشاركين في المجموعة uses a more explicit existential style: There are nine participants in the group

Both are acceptable, but the original is a very common Arabic way to express the idea.

The singular is:

• مشارك = participant (masculine)

Its plural here is:

• مشاركون / مشاركين

This word comes from the verb شارك meaning to participate or to take part.

Related forms:

• مشارك = a male participant
• مشاركة = a female participant
• مشاركون = participants (masculine plural, nominative)
• مشاركين = participants (masculine plural, accusative/genitive)
• مشاركات = female participants / feminine plural participants