kyou ha hakubutukan ga yasumi desu.

It is read:

きょう は はくぶつかん が やすみ です。

Word by word:

• 今日 = きょう
• 博物館 = はくぶつかん
• 休み = やすみ

A small note: 今日 is not read こんにち here. In this sentence, it is きょう, meaning today.

Here, は marks 今日 as the topic: as for today.

So 今日は gives a feeling like:

• Today, ...
• As for today, ...

You usually do not use に with common time words like 今日, 明日, and 昨日 in this kind of sentence.

So:

• 今日は博物館が休みです。 = natural
• 今日に博物館が休みです。 = not natural here

Because they are doing different jobs.

• は marks the topic: 今日 = today
• が marks the thing being described: 博物館 = the museum

So the structure is roughly:

• As for today, the museum is closed.

Japanese often has both a topic and a subject in the same sentence.

博物館が休みです is a natural way to say that the museum is the thing that is closed within the frame of today.

Using が can sound like the museum is the item being identified:

• What is closed today?
• The museum is.

If you say 博物館は休みです, that is also possible, but the nuance shifts a little:

• 博物館は休みです。 = As for the museum, it is closed.

So both can work, but the focus is slightly different.

休み is a noun here, not a verb.

It comes from the verb 休む meaning to rest / to take a break / to be absent.

In this sentence, 休み means something like:

• a day off
• a rest day
• for a place like a museum, closed

So 博物館が休みです literally feels closer to:

• The museum is on a rest day.

That is why it gets translated naturally as The museum is closed.

Japanese often expresses this idea with 休みです instead of a verb.

For places, shops, schools, and businesses, 休みです often means:

• not open today
• closed today

This is a little different from saying something is physically shut.

For example:

• 休みです = closed for business / not operating
• 閉まっています = physically shut

For a museum specifically, you may also see the more formal word 休館:

• 今日は博物館が休館です。

That is especially common in signs or formal announcements.

です makes the sentence polite.

It is the polite copula, similar to is/am/are in some situations, though it does not match English exactly.

So:

• 休みです = polite
• 休みだ = plain
• 休み = plain, often used casually in conversation

In this sentence, です is simply making the statement polite and complete.

Yes, to some extent. Japanese word order is more flexible than English, as long as the particles make the roles clear.

For example:

• 今日は博物館が休みです。
• 博物館は今日休みです。
• 今日は博物館は休みです。

These are all possible, but the emphasis changes.

Very roughly:

• 今日は博物館が休みです。 = As for today, the museum is closed.
• 博物館は今日休みです。 = As for the museum, it is closed today.
• 今日は博物館は休みです。 = Today, the museum is closed; this can sound a bit contrastive depending on context.

The main thing that usually stays the same is that the predicate comes at the end: 休みです.

Japanese does not have articles like a, an, or the.

So 博物館 can mean:

• a museum
• the museum

The exact meaning depends on context.

In this sentence, English naturally uses the museum, but Japanese does not need a separate word for that.

Those spaces are usually just for learners.

Normal Japanese is written without spaces:

今日は博物館が休みです。

Textbooks and beginner materials sometimes add spaces to make it easier to see the parts of the sentence.