المترجم في الندوة.

Because in Arabic, the verb to be is usually not stated in the present tense.

So:

• المترجم = the translator
• في الندوة = at/in the seminar

Together, المترجم في الندوة means The translator is at the seminar.

This is very normal in both Standard Arabic and Egyptian-style usage.
If you wanted a past or future meaning, then Arabic would use an actual verb:

• كان المترجم في الندوة = The translator was at the seminar
• هيكون المترجم في الندوة (Egyptian) = The translator will be at the seminar

It can be understood as a full sentence: The translator is at the seminar.

But without context, Arabic strings like this can sometimes also feel a little phrase-like, especially in isolation. In normal use, though, a reader will usually take it as a complete nominal sentence:

• المترجم = the topic / subject
• في الندوة = the information about where he is

So grammatically, it works perfectly as a sentence.

Because each one refers to a specific, known thing:

• المترجم = the translator
• الندوة = the seminar

Arabic uses the prefix الـ to mean the.

So:

• مترجم = a translator
• المترجم = the translator
• ندوة = a seminar / symposium
• الندوة = the seminar / the symposium

There is nothing strange about having two definite nouns in one sentence here, because one is the subject and the other is inside a prepositional phrase:

• المترجم = the subject
• في الندوة = in the seminar / at the seminar

Great question. الندوة is written with ال, but it is pronounced with assimilation because ن is a sun letter.

So:

• written: الندوة
• pronounced roughly: en-nadwa (or an-nadwa in more formal pronunciation)

The ل of ال blends into the ن sound.

That means:

• المدرسة → el-madrasa / al-madrasa because م is not a sun letter
• الندوة → en-nadwa / an-nadwa because ن is a sun letter

In Egyptian pronunciation, a learner will often hear something close to en-nadwa.

A natural Egyptian-style pronunciation would be roughly:

el-motargem fi n-nadwa
or
el-motarjem fi n-nadwa

A few notes:

• المترجم is often pronounced something like el-motargem / el-motarjem
• في is fi
• الندوة becomes en-nadwa or just with the merged n-nadwa

So the whole sentence may sound smoother in connected speech than the spelling suggests.

Here في can often be translated as either in or at, depending on natural English.

Basic meaning:

• في = in

But with events or places, English often prefers at:

• في البيت = in the house
• في المدرسة = at school / in the school
• في الندوة = at the seminar

So in this sentence, at the seminar is usually the most natural English translation, even though في literally means in.

It is understandable, but it sounds a bit formal.

ندوة usually means something like:

• seminar
• symposium
• panel discussion

In everyday Egyptian speech, people might also use other words depending on the situation, such as:

• محاضرة = lecture
• اجتماع = meeting
• even borrowed words like سيمنار in some contexts

So the structure of the sentence is fine, but the word ندوة has a somewhat formal or literary feel.

Yes. Arabic often starts nominal sentences with the thing being talked about.

So:

• المترجم في الندوة = The translator is at the seminar

This is the most straightforward order if you want to talk about the translator.

You can sometimes change word order for emphasis, for example:

• في الندوة المترجم

But that sounds more marked and less neutral in isolation. For a learner, المترجم في الندوة is the normal pattern to remember.

A common Egyptian negative would be:

المترجم مش في الندوة
= The translator is not at the seminar

Here:

• مش = not

This is the usual Egyptian way to negate this kind of present-tense nominal sentence.

Compare:

• المترجم في الندوة = The translator is at the seminar
• المترجم مش في الندوة = The translator is not at the seminar

If you remove الـ, you get:

مترجم في الندوة

That can mean something like:

• a translator is at the seminar
• or, depending on context, it may sound less complete or less natural

Arabic often handles indefiniteness differently from English, and an indefinite subject at the beginning can be less straightforward than a definite one.

So for beginners, the definite version:

المترجم في الندوة

is simpler and more natural as a clear sentence meaning The translator is at the seminar.

It sits a bit between the two, but it looks more Standard Arabic in writing.

Why?

• The spelling is standard Arabic spelling.
• The structure is valid in both Standard Arabic and Egyptian.
• The word ندوة feels somewhat formal, which leans toward Standard Arabic or formal speech.

In spoken Egyptian, the pronunciation would shift, and people might choose a different word for seminar depending on context. But an Egyptian speaker would still understand this sentence easily.