kaeri no densya de tomodati kara no messeezi wo yomimasita.

帰り here is a noun, not a plain verb form.

It comes from 帰る (to return / to go home), but 帰り means something like:

• the return
• the way back
• the trip home

So in this sentence, 帰りの電車 means the train on the way back / the train home.

A common learner mistake is to think this is just the -masu stem of 帰る, but in many cases that stem also functions as a noun.

The の connects 帰り and 電車 so that 帰り describes what kind of train it is.

So:

• 帰り = the return / the way home
• 電車 = train
• 帰りの電車 = the train home / the train on the way back

This is a very common use of の: one noun modifies another noun.

Other similar patterns:

• 日本の車 = a Japanese car / a car from Japan
• 学校の先生 = a school teacher / the teacher at school
• 朝の電車 = the morning train

So here, 帰りの電車 is a noun phrase built with noun + の + noun.

In this sentence, で is most naturally understood as marking the place where the action happened:

• 帰りの電車で = on the train home

So the message was read while on the train.

It is true that で can also mark means/method, as in:

• 電車で行く = go by train

But in this sentence, because the action is 読む (to read), 電車で is better understood as the setting/location where the reading happened, not the transportation method used to read.

So:

• 電車で行きました = I went by train
• 電車で読みました = I read it on the train

This is a very important pattern.

• から means from
• の lets the whole phrase 友達から modify the noun メッセージ

So:

• 友達からのメッセージ = a message from a friend

You can think of it like this:

1. 友達から = from a friend
2. add の so that it can attach to a noun
3. 友達からのメッセージ = a message from a friend

This pattern is common:

• 先生からのメール = an email from the teacher
• 会社からのお知らせ = a notice from the company
• 彼からの電話 = a phone call from him

Because 友達から by itself is a particle phrase, and if you want it to directly modify a noun, Japanese usually uses の.

So:

• 友達からのメッセージ = correct
• 友達からメッセージ = incomplete/unnatural as a noun phrase

However, 友達から can connect directly to a verb, for example:

• 友達からメッセージをもらいました = I got a message from a friend
• 友達から連絡がありました = I got contacted by a friend

So the key difference is:

• 友達からのメッセージ → from a friend modifies message
• 友達からメッセージをもらいました → from a friend modifies the whole event

Good question. They are similar, but the nuance is different.

友達からのメッセージ

This clearly means:

• a message from a friend

It emphasizes the source/sender.

友達のメッセージ

This can also sometimes mean your friend’s message, but it is less explicitly from in the sense of sender. Depending on context, it may sound more like:

• the message belonging to the friend
• the friend’s message
• the message the friend wrote

So if you specifically want to say from a friend, 友達からのメッセージ is the safer and clearer choice.

を marks the direct object of the verb.

Here:

• 友達からのメッセージ = the message from a friend
• を = object marker
• 読みました = read

So メッセージを読みました means:

• read the message

This is the standard pattern:

• 本を読む = read a book
• 新聞を読む = read the newspaper
• メッセージを読む = read a message

Because the sentence is describing a completed action:

• I read a message...

So Japanese uses the polite past form:

• 読む = read / will read
• 読みます = read / will read (polite)
• 読みました = read (polite past)

Even if the English translation is something like I read it on the train home, Japanese often uses the past tense simply because the event happened and is complete.

Because Japanese often omits the subject when it is clear from context.

So even though English usually needs I, Japanese often does not say it if the speaker is obviously talking about their own experience.

This sentence naturally implies:

• (I) read a message from a friend on the train home.

Adding 私は is possible, but it is often unnecessary unless you want contrast or emphasis.

For example:

• 私は帰りの電車で友達からのメッセージを読みました。

This is grammatical, but it sounds a little more explicit than the original.

The basic meaning stays the same as long as the particles stay attached to the right words.

Original:

• 帰りの電車で友達からのメッセージを読みました。

You could also say:

• 友達からのメッセージを帰りの電車で読みました。

Both are natural. The difference is mainly focus:

• 帰りの電車で... first → sets the scene first
• 友達からのメッセージを... first → focuses first on what was read

Japanese word order is more flexible than English, but the verb usually comes at the end.

It can feel like either one in English, depending on context.

Literally, it is the return train or the train on the way back, but natural English often translates it as:

• on the train home
• on the way home by train
• on the train back

In real usage, the Japanese phrase often refers less to a specific train vehicle and more to the situation of being on the train while going home.

So the English translation may vary a little, even though the Japanese is straightforward.

You could make a sentence with 帰りに, but it is not exactly the same structure or nuance.

帰りの電車で

This means:

• on the train home
• it specifically places the action in the return train

帰りに

This means:

• on the way back
• while returning
• on my way home

So:

• 帰りに友達からのメッセージを読みました。
  = I read a message from a friend on the way home.

This is broader and does not specifically say on the train.

If you say:

• 帰りに電車で...

that can sound like you are stacking two separate ideas:

• on the way back
• by train / on the train

It is not impossible, but 帰りの電車で is a cleaner way to say on the train home.

Both can mean friend, but the nuance is different.

• 友達 = common, casual, everyday word
• 友人 = more formal or written

Since メッセージ is also a common, everyday word, 友達 fits the natural tone of the sentence very well.

So this sentence sounds like normal spoken or casual written Japanese.

Yes, メッセージ is a loanword from English message.

In modern Japanese, メッセージ is very common for things like:

• text messages
• app messages
• written digital messages

Depending on context, other words are possible, such as:

• メール = email, sometimes also text-like messaging in older usage
• 連絡 = contact / communication
• 手紙 = letter

But メッセージ is very natural if the sentence is about reading a message on a phone or app.

Those spaces are usually just for learning purposes.

Normal Japanese writing would typically be:

• 帰りの電車で友達からのメッセージを読みました。

Japanese does not normally put spaces between words the way English does. Textbooks and beginner materials often add spaces to help learners see the parts more clearly.

So the spaced version is not wrong as a teaching tool, but the standard written sentence has no spaces.

Yes:

• 帰りの電車で = on the train home
• 友達からのメッセージを = a message from a friend
• 読みました = read

So the structure is:

• [place/setting] + [object] + [verb]

More literally:

• On the return train, [I] read a message from a friend.

That chunking can make the sentence much easier to process.