matiaisitu de hon wo yominagara, zibun no ban wo matte imasita.

待合室 is read まちあいしつ.

It means waiting room.

It is made of:

• 待 = wait
• 合 = together / mutual
• 室 = room

So it is literally something like a room for waiting.

The particle で marks the place where an action happens.

In this sentence, the actions are:

• 本を読む = read a book
• 番を待つ = wait for one’s turn

Both actions happen in the waiting room, so 待合室で means in the waiting room.

Compare:

• 待合室で読む = read in the waiting room
• 待合室に行く = go to the waiting room

So で is used because this is the location of the action, not the destination.

Because 本 is the direct object of the verb 読む.

• 本を読む = read a book / read the book

The particle を marks what is being read.

Using が here would not work, because 本 is not the thing doing the reading. The subject is omitted, but it is understood to be the speaker or some other person being talked about.

読みながら means while reading.

It comes from:

• 読む = to read
• stem form 読み
• ながら = while doing

So:

• 本を読みながら = while reading a book

This pattern shows that two actions are happening at the same time.

In this sentence:

• reading a book
• waiting for one’s turn

Both are happening together.

Yes. A very important rule is that the same person does both actions.

So in this sentence, the person who is:

• reading the book is also the person who is
• waiting for their turn

That is why this sentence naturally means something like:

• I was waiting for my turn while reading a book or
• He/She was waiting for their turn while reading a book

depending on context.

Also, the main action usually comes at the end of the sentence. Here, the main action is:

• 待っていました = was waiting

自分の番 means one’s own turn or my turn / your turn / his turn, depending on context.

Breakdown:

• 自分 = oneself
• の = possession / linking particle
• 番 = turn

So literally:

• 自分の番 = one’s own turn

In many contexts, 自分 can mean:

• myself
• yourself
• himself / herself

But in a sentence like this, it often naturally means my turn if the speaker is talking about their own experience.

Because 自分の番 is a set, natural way to say one’s own turn.

You could also say:

• 私の番 = my turn

But 自分の番 can sound a little more neutral or less directly self-focused, depending on context.

In many cases:

• 私の番を待っていました would sound a bit less natural
• 自分の番を待っていました sounds very natural

This is because Japanese often uses expressions that focus on the situation rather than explicitly saying I.

待つ can be used for many things, not just people.

You can wait for:

• a person
• a bus
• a reply
• a chance
• your turn

So:

• 番を待つ = wait for one’s turn

This is a very common expression.

Examples:

• 順番を待つ = wait your turn
• バスを待つ = wait for the bus
• 返事を待つ = wait for a reply

They are similar, but not exactly the same.

• 番 = turn
• 順番 = order / turn in sequence

In many everyday situations, both can work.

For example:

• 自分の番を待つ = wait for your turn
• 自分の順番を待つ = wait for your turn

順番 emphasizes the idea of order in a line or sequence a little more.

番 is shorter and very common in expressions like:

• 私の番です = It’s my turn
• 次はあなたの番です = You’re next

待っていました is the past progressive (or past continuous) polite form of 待つ.

• 待つ = wait
• 待っている = be waiting
• 待っていました = was waiting

This fits the sentence well because it describes an ongoing situation in the past:

• the person was sitting there
• reading a book
• and waiting for their turn

If you said 待ちました, that would simply mean waited, without focusing as much on the continuing action.

So:

• 待ちました = waited
• 待っていました = was waiting

In this sentence, was waiting matches the feeling better.

Both are possible, but they differ in politeness.

• 待っていた = casual plain form
• 待っていました = polite form

The sentence you were given is in polite style, so いました is used.

The rest of the sentence also matches polite spoken/written Japanese:

• 待っていました sounds polite and natural

If the whole sentence were casual, it could be:

• 待合室で本を読みながら、自分の番を待っていた。

Japanese often leaves out the subject when it is clear from context.

So this sentence does not explicitly say:

• I
• he
• she
• we

The subject must be understood from the situation.

Depending on context, it could mean:

• I was waiting for my turn while reading a book in the waiting room.
• He was waiting for his turn while reading a book in the waiting room.
• She was waiting for her turn while reading a book in the waiting room.

If this is someone describing their own experience, the most natural interpretation is often I.

The comma helps separate the while-reading part from the main action.

So the structure is easier to see:

• 待合室で = in the waiting room
• 本を読みながら = while reading a book
• 自分の番を待っていました = was waiting for my/one’s turn

The comma is not absolutely required in every case, but it is very common and makes the sentence easier to read.

Yes, that is a very close literal translation.

A more natural English version might be:

• I was reading a book in the waiting room while waiting for my turn.
• I waited for my turn in the waiting room while reading a book.
• I was waiting for my turn in the waiting room, reading a book.

Japanese often puts the background action first and the main action last, which is why the sentence ends with 待っていました.