Секционное заседание проходит в главном зале.

Секционное заседание is in the nominative case because it is the subject of the sentence — the thing that is happening.

• заседание is a neuter singular noun.
• The adjective секционное has to agree with it in:
  • gender: neuter
  • number: singular
  • case: nominative

So:

• секционный = masculine
• секционная = feminine
• секционное = neuter

Because заседание is neuter, the adjective must also be neuter: секционное заседание.

Because the subject, заседание, is singular.

Проходит is the 3rd person singular present tense form of проходить.

So the structure is:

• заседание = the meeting/session
• проходит = takes place / is being held

If the subject were plural, the verb would also be plural:

• Секционные заседания проходят... = Section meetings take place...

That is a very common question. Russian verbs often have several related meanings depending on context.

Проходить can mean things like:

• to pass
• to go through
• to take place
• to be held

In this sentence, because the subject is заседание (a meeting/session), the natural meaning is:

• Заседание проходит... = The session is taking place... / The session is being held...

This use is very common with events:

• Концерт проходит в театре. = The concert takes place in the theater.
• Выставка проходит в музее. = The exhibition is being held in the museum.

Here в takes the prepositional case because it shows location: in the main hall.

So:

• зал = hall
• в зале = in the hall

And the adjective must match:

• главный зал = main hall
• в главном зале = in the main hall

So both words are in the prepositional singular:

• главном
• зале

A useful comparison:

• в зал = into the hall (accusative, movement toward)
• в зале = in the hall (prepositional, location)

Because after в meaning in a place, Russian usually uses the prepositional case, not the nominative.

The dictionary form is:

• главный зал = main hall

But in the sentence we need in the main hall, so both words change:

• главный → главном
• зал → зале

This is adjective-noun agreement again: the adjective changes to match the noun’s case, number, and gender.

Yes, it is a normal formal or academic expression.

Секционное comes from секция, which often means section, division, or panel/group within a larger conference or event.

So секционное заседание usually means something like:

• a section meeting
• a panel session
• a breakout session

It is more formal than everyday conversation and is often used in conference, academic, or official contexts.

Russian has no articles — no direct equivalents of a/an and the.

So:

• заседание can mean a session or the session
• в главном зале can mean in the main hall

Russian shows definiteness through context, word order, intonation, and the situation, not through articles.

This is something English speakers have to get used to: Russian normally does not mark a/the at all.

Yes. Russian word order is more flexible than English word order because grammatical endings show the relationships between words.

The neutral order here is:

• Секционное заседание проходит в главном зале.

But other orders are possible, for example:

• В главном зале проходит секционное заседание.
• Проходит секционное заседание в главном зале.

These alternatives may sound more natural in certain contexts, especially if you want to emphasize where it is happening.

Still, the original sentence is a very standard, neutral way to say it.

Russian often uses the present tense where English uses either:

• a simple present: takes place
• or a present progressive/passive-type expression: is being held

So:

• проходит literally looks like passes / goes on
• but in context it means is taking place or is being held

Russian does not form this idea the same way English does. You do not need a separate form for is being held here.

Проходить is imperfective.

That makes sense because the sentence describes an event as:

• ongoing,
• currently happening,
• or generally taking place.

Imperfective is commonly used for processes and events in progress:

• Заседание проходит... = The session is taking place...

The perfective partner is often пройти, but that would not be used here in the same way for a current ongoing event.

Sometimes, yes, but the style changes.

Russian can use идти with events in the sense of to be going on:

• Заседание идёт. = The session is underway.

But проходит is especially common in formal contexts for:

• meetings
• conferences
• exhibitions
• concerts
• lessons
• events

So in a formal sentence like this, проходит sounds very natural.

You learn it as part of noun declension patterns.

The noun зал is a masculine inanimate noun. Its basic forms include:

• nominative: зал
• accusative: зал
• prepositional: зале

So after в meaning in, you get:

• в зале

This is a very common pattern for masculine nouns:

• в музее = in the museum
• в театре = in the theater
• в зале = in the hall

Not every noun follows exactly the same pattern, but this is a common one.

It sounds neutral-to-formal.

Reasons:

• секционное заседание is a formal expression
• проходит is often used in official or informational descriptions of events
• в главном зале is straightforward and neutral

This is the kind of sentence you might see in:

• a conference program
• an announcement
• a schedule
• an event description

It is correct and natural, but not especially casual.