يسجل المشارك في المؤتمر.

Arabic often uses verb–subject word order, especially in simple statements.

So:

• يسجل المشارك في المؤتمر. = The participant registers at the conference.

This is a very normal Arabic sentence pattern:

• يسجل = the verb
• المشارك = the subject
• في المؤتمر = a prepositional phrase

You could also say:

• المشارك يسجل في المؤتمر.

That puts more emphasis on the participant. Both are grammatical, but the original sentence uses the very common verbal sentence pattern.

Here يسجل means registers, signs up, or checks in, depending on context.

The verb comes from سجّل and can have meanings like:

• to register
• to record
• to write down
• to enroll

In this sentence, because of المشارك and المؤتمر, the most natural meaning is registers or checks in.

So the sentence is understood as something like:

• The participant registers at the conference.

Yes. In full vocalization, this verb would be written:

• يُسَجِّلُ

The shadda on ج is important in fully marked text because the verb is from Form II سجّل.

But in ordinary Arabic writing, short vowels and signs like shadda are often omitted, so you commonly see:

• يسجل

Even without the marks, a reader is expected to recognize it from context.

Yes. يسجل is in the imperfect form, which often corresponds to the present tense in English.

Depending on context, it can mean:

• registers
• is registering
• will register

Without extra context, English often translates it as a simple present:

• The participant registers at the conference.

But if the situation is happening now, it could also be understood as:

• The participant is registering at the conference.

Arabic imperfect verbs are often more flexible than English present-tense forms.

المشارك means the participant.

It is related to the verb شارك = to participate.

More specifically, مشارك is an active participle, meaning literally something like:

• participating
• one who participates

As a noun, it commonly means:

• participant

So:

• المشارك = the participant

الـ is the Arabic definite article, meaning the.

So:

• مشارك = a participant / participant
• المشارك = the participant

Since the English meaning already has the participant, Arabic uses الـ to show that the noun is definite.

In Arabic, the subject does not have to come before the verb.

In a verbal sentence, the normal order is often:

• verb + subject + other information

So in:

• يسجل المشارك في المؤتمر

the subject is المشارك, even though it comes after the verb.

If the sentence were fully vowelled, the subject would show nominative case:

• يُسَجِّلُ المُشارِكُ في المُؤتَمَرِ

The ending ـُ on المشاركُ marks it as the subject.

Literally, في often means in.

So word-for-word:

• في المؤتمر = in the conference

But in natural English, with an event like a conference, this is usually translated as:

• at the conference

So the phrase can be understood as:

• at the conference
• sometimes in the conference, depending on context

In normal English, at the conference is usually the best translation.

Because في is a preposition, and prepositions are followed by a noun.

So:

• في = in / at
• المؤتمر = the conference

Together:

• في المؤتمر = at the conference

Also, after a preposition, the noun is in the genitive case. In fully vowelled Arabic:

• في المُؤتَمَرِ

The ending ـِ shows the genitive after في.

It is pronounced approximately:

• al-muʾtamar

A more careful breakdown:

• ال = al-
• مؤ = muʾ
• تمر = tamar

The small break in muʾ comes from the hamza (ء).

So the full phrase is approximately:

• yusajjilu al-mushāriku fī al-muʾtamar

المؤتمر comes from the root:

• أ م ر

This root is often connected with meanings involving command, matter, or affair.

As a vocabulary item, though, the important thing for learners is simply that:

• مؤتمر = conference

You do not need to analyze the root in order to understand or use the sentence, but it can help you recognize related words later.

In theory, يسجل can mean records or writes down, because the verb has more than one meaning.

But in this sentence, the context strongly points to registers:

• المشارك = the participant
• في المؤتمر = at the conference

That combination makes registers/checks in the most natural meaning.

If the intended meaning were records, Arabic would usually provide a clearer object, such as:

• يسجل المشارك الملاحظات = The participant records the notes

If the subject were feminine, both the noun and the verb would change.

For example:

• تسجل المشاركة في المؤتمر.

This means:

• The female participant registers at the conference.

Changes:

• يسجل → تسجل
• المشارك → المشاركة

So the verb agrees with the gender of the subject.

Yes.

You can say:

• المشارك يسجل في المؤتمر.

This still means:

• The participant registers at the conference.

The difference is mainly one of style or emphasis:

• يسجل المشارك في المؤتمر = neutral verbal sentence, very common
• المشارك يسجل في المؤتمر = starts with the subject, often giving it a little more focus

Both are correct.