Этот бутон ещё закрыт.

Because бутон is a masculine singular noun.

In Russian, demonstratives like this must agree with the noun in gender, number, and case:

• этот = masculine singular
• эта = feminine singular
• это = neuter singular
• эти = plural

Since бутон is masculine singular, the correct form is этот бутон.

It is in the nominative case.

That is because бутон is the subject of the sentence — the thing being described as closed.

So the structure is basically:

• Этот бутон = the subject
• ещё закрыт = what is being said about it

In Russian, the verb to be is usually not expressed in the present tense.

So English:

• This bud is still closed.

becomes Russian:

• Этот бутон ещё закрыт.

Russian does use forms of to be in the past and future, but in the present tense it is normally omitted.

So the sentence literally looks like:

• This bud still closed.

but it naturally means This bud is still closed.

Here ещё means still.

So:

• Этот бутон закрыт = This bud is closed
• Этот бутон ещё закрыт = This bud is still closed

It adds the idea that the state continues up to now.

A very common learner confusion is that ещё can also mean more / another in other contexts, but here it clearly means still.

Because закрыт is the form used after the subject to describe its current state.

Compare:

• закрытый бутон = a closed bud
  
  • here закрытый is a full adjective-like form used before the noun
• бутон закрыт = the bud is closed
  
  • here закрыт is the short form used as the predicate

So in this sentence, Russian prefers:

• Этот бутон ещё закрыт.

not:

• Этот бутон ещё закрытый. (usually unnatural here)

Yes, it agrees with бутон in gender and number.

Here are the short-form endings:

• masculine: закрыт
• feminine: закрыта
• neuter: закрыто
• plural: закрыты

Because бутон is masculine singular, the sentence uses закрыт.

For example:

• Дверь закрыта. = The door is closed.
• Окно закрыто. = The window is closed.
• Цветы закрыты. = The flowers are closed.

For a learner, the most useful way to think about it is: it behaves like a predicate adjective describing a state.

Historically and grammatically, it is connected with a short-form passive participle/adjective, but in everyday learning it is enough to understand:

• закрыт = closed, describing the current condition of something

So this sentence is about the state of the bud, not the action of someone closing it.

If you wanted an action idea, Russian would use something different, for example a verb meaning is closing or opens/closes depending on context.

Yes, Russian word order is flexible, but Этот бутон ещё закрыт is the most neutral and natural order here.

This order works like:

• Этот бутон = topic / subject
• ещё закрыт = comment about it

You may see other orders in context for emphasis, but they can sound more marked. For example:

• Этот бутон ещё закрыт. = neutral
• Ещё закрыт этот бутон. = more emphatic or literary, depending on context

For a learner, the given order is the best one to use first.

The normal stress is:

• Э́тот буто́н ещё́ закры́т.

A rough pronunciation guide:

• этот ≈ EH-tuht
• бутон ≈ boo-TON
• ещё ≈ yi-SHCHO
• закрыт ≈ zuh-KRIT

A few helpful notes:

• ё is always stressed when written: ещё
• In real texts, ё is sometimes written as е, so you may see еще, but it is still pronounced ещё

Yes, бутон usually means a bud, especially a flower bud.

So in this sentence, it suggests a bud that has not opened yet.

Depending on context, Russian can use other plant-related words, but бутон is the normal word for a blossom/flower bud.

Yes. In this sentence, closed is the most natural English choice, but shut is also possible depending on style.

So:

• Этот бутон ещё закрыт.
  = This bud is still closed.

For a flower bud, closed sounds more natural than shut in most contexts.