Оргкомитет отправил письмо участникам.

Because the subject оргкомитет is a masculine singular noun in Russian.

In the past tense, Russian verbs agree with the subject in gender and number:

• masculine: отправил
• feminine: отправила
• neuter: отправило
• plural: отправили

So:

• Оргкомитет отправил... = The organizing committee sent...

Even though a committee is made up of several people, оргкомитет is grammatically singular, so the verb is singular too.

Оргкомитет is a shortened form of организационный комитет, meaning organizing committee or organizing committee staff/body.

Russian often uses shortened compound words like this, especially in formal or institutional contexts.

So:

• организационный комитет = full form
• оргкомитет = common shortened form

Письмо is the direct object of the verb отправил, so it is in the accusative case.

However, for many inanimate neuter nouns, the nominative and accusative forms are the same.

So:

• nominative: письмо
• accusative: письмо

That is why there is no visible ending change.

Because участникам is in the dative plural.

The sentence uses участникам to mean to the participants — the people who received the letter.

The base noun is:

• участник = participant

Its plural forms include:

• nominative plural: участники = participants
• dative plural: участникам = to the participants

The ending -ам is a very common dative plural ending for masculine nouns.

Because Russian often expresses to someone by using the dative case, without needing a separate word like English to.

So in this sentence:

• письмо участникам literally means something like a letter to participants

This is very normal in Russian. The case ending itself carries the meaning that English often shows with a preposition.

Отправить is perfective.

That matters because the perfective aspect presents the action as completed: the letter was sent successfully as a finished event.

So:

• отправил = sent / has sent in the sense of a completed action

Compare:

• отправил письмо = sent the letter, completed
• отправлял письмо = was sending / used to send / sent (with focus on process or repeated action, depending on context)

In this sentence, the perfective form is natural because it describes one completed act.

Yes, but the meaning would change.

• Оргкомитет отправил письмо участникам.
  The organizing committee sent the letter.
  Focus: completed action.

• Оргкомитет отправлял письмо участникам.
  The organizing committee was sending / used to send / sent the letter.
  Focus: process, repetition, or background action, depending on context.

Without extra context, отправил is the more straightforward choice for a single completed event.

Because Russian has no articles.

English must choose between things like:

• a letter
• the letter
• the participants

Russian does not use separate words for that. Instead, definiteness is usually understood from:

• context
• word order
• the situation
• intonation

So письмо can mean a letter or the letter, depending on context.

No. Russian word order is more flexible than English word order because case endings show grammatical roles.

The neutral, straightforward order here is:

• Оргкомитет отправил письмо участникам.

But other orders are possible, for example:

• Письмо оргкомитет отправил участникам.
• Участникам оргкомитет отправил письмо.

These alternatives change emphasis or information structure, not the basic core meaning.

English usually relies much more on word order to show who did what to whom.

Russian uses case and verb agreement to make this clear.

In this sentence:

• оргкомитет is in the nominative, so it is the subject
• письмо is the direct object
• участникам is in the dative, so it is the recipient

So the structure is:

• [subject] оргкомитет
• [verb] отправил
• [thing sent] письмо
• [recipient] участникам

Even if the word order changes, these endings still help you identify each role.

It is plural.

The singular forms would be:

• участник = participant
• участнику = to the participant

But here we have:

• участникам = to the participants

So the sentence says the letter was sent to more than one participant.

Sometimes, yes, depending on context.

Most basically, письмо means letter. But in modern Russian it can also refer to a written message, including an email, especially if the context makes that clear.

For clarity, people may also say:

• электронное письмо = email
• имейл / email = email

So in isolation, many learners will understand письмо as a physical letter, but context could broaden the meaning.

The main stress is:

• оргкомите́т
• отпра́вил
• письмо́
• уча́стникам

A rough pronunciation guide:

• оргкомите́т ≈ org-ka-mee-TYET
• отпра́вил ≈ at-PRA-vil
• письмо́ ≈ pees-MO
• уча́стникам ≈ oo-CHAST-nee-kam

Stress is very important in Russian, because it is not always predictable and can affect pronunciation of vowels.

Because участников would be a different case with a different meaning.

Compare:

• участникам = to the participants → dative plural
• участников = participants in the genitive plural or animate accusative plural, depending on context

After отправить письмо кому? the recipient goes in the dative, so участникам is correct.

For example:

• отправить письмо участникам = send a letter to the participants

not

• отправить письмо участников = that would suggest something like the participants’ letter, which is a different structure entirely.

The pattern is:

[Subject] + [verb] + [direct object] + [recipient in dative]

So here:

• Оргкомитет = subject
• отправил = verb
• письмо = direct object
• участникам = indirect object / recipient

This is a very useful pattern to learn for verbs like:

• дать = to give
• показать = to show
• послать / отправить = to send
• передать = to pass on / hand over

For example:

• Она дала книгу студентам.
• Он отправил документы клиенту.

So this sentence is a good model for a common Russian structure.