Learn Hardcore Japanese: tomodati kara messeezi wo morau to, totemo uresii desu. - When I receive a message from a friend, I am very happy.

Depending on the situation, the implied subject could also be you, we, or people in general, but in a typical textbook context it is read as I.

Leaving out the subject is a very natural feature of Japanese; you only say it when you need to clarify who you are talking about.

What does から mean after 友達? What does 友達から express?

から here means from and marks the source of an action or thing.

友達から = from (a) friend / from friends
友達からメッセージをもらう = receive a message from a friend (or from friends)

More generally, から can mark:

a source: 田中さんから本をもらいました – I got a book from Tanaka.
a starting point in time or space:
９時から – from 9 o’clock
東京から大阪まで – from Tokyo to Osaka

In this sentence it’s clearly “from (the) friend(s).”

Could we say 友達にメッセージをもらう instead of 友達からメッセージをもらう? Is there a difference?

Yes, 友達にメッセージをもらう is also grammatically correct and natural.

With もらう, the person you receive something from can be marked by either に or から:

友達にメッセージをもらう
友達からメッセージをもらう

Both mean “receive a message from a friend.”

Nuance:

に is very common with もらう and can feel a bit more neutral.
から explicitly highlights the idea of “from (this source)”, and can feel just a bit more “source-focused.”

In everyday speech, both are widely used; in many contexts they are interchangeable.

Why do we use the particle を after メッセージ?

を marks the direct object of a verb – the thing the action is done to.

The basic pattern with もらう is:

[receiver] は [giver] に / から [thing] をもらう
= [receiver] receives [thing] from [giver].

So here:

メッセージ = the thing being received (direct object)
メッセージをもらう = to receive a message

That is why メッセージ takes を.

What is the と after もらう doing? Is this the same と as in quoting things?

Here と is not the quotative と. It is the conditional と, which means something like “when(ever) / if”.

Structure:

[plain verb] と、[result / natural consequence]

Meaning:
Whenever / if the first action happens, the second naturally follows.

So:

友達からメッセージをもらうと
= When(ever) I receive a message from a friend,
とてもうれしいです
= I am very happy.

Together:
Whenever / when I get a message from a friend, I feel very happy.

So this と creates a cause→result / condition→result relationship, not reported speech.

Could we say メッセージをもらったら or メッセージをもらうとき instead of メッセージをもらうと? What’s the difference?

All three can be used, but the nuance changes.

メッセージをもらうと、とてもうれしいです。
- と conditional:
- Feels like a general rule / automatic reaction.
- “Whenever I get a message from a friend, I (always) feel very happy.”
メッセージをもらったら、とてもうれしいです。
- 〜たら conditional:
- Feels more like “if / when (it happens at some time)”.
- Often used for specific situations or one-time events, though it can also be general.
- “If / when I get a message from a friend, I’m very happy.”
メッセージをもらうとき、とてもうれしいです。
- 〜とき = “when / at the time (that)”
- Focuses on the time of the action itself.
- Slightly different nuance; sounds a bit odd here, because うれしい is more of the emotional result than something you feel during the exact moment of receiving.
- More natural would be something like:
  メッセージをもらったとき、とてもうれしかったです。
  “When I got the message, I was very happy.” (a specific past event)

For a general, habitual feeling, 〜と is a very good choice.

Is it okay that もらう is in plain form but うれしいです is polite? Isn’t mixing styles bad?

In this case, it is perfectly natural and correct.

In Japanese, it is common for:

The main clause to carry the politeness level,
While subordinate clauses (like conditionals) use the plain form.

So:

Subordinate conditional clause (plain):
友達からメッセージをもらうと、
Main clause (polite):
とてもうれしいです。

If you tried to make the first verb polite:

友達からメッセージをもらいますと、とてもうれしいです。

this is technically possible but sounds stiff/formal and not natural in everyday speech. The original sentence is more natural.

So: Yes, this “mix” is normal, because it’s not really mixing styles inside the same clause; it’s using plain form in a subordinate clause and polite form in the main clause.

What exactly does とても mean here? Is it like “very”? Could I use すごく instead?

とても is an adverb meaning roughly “very” / “really”.

とてもうれしいです。
= I’m very happy.

Nuance:

とても: neutral, polite, common in both spoken and written Japanese.
すごく: a bit more casual / colloquial, often heard in speech:
- すごくうれしいです。 – also fine; slightly more informal-feeling.
本当にうれしいです。 – “I’m truly / really happy.” (emphasizes sincerity)

In a textbook-style polite sentence, とても is a very standard and safe choice.

Why is it うれしいです and not something like うれしいだ?

うれしい is an i-adjective (形容詞).
The rules are:

i-adjectives: [adjective] + です for polite speech
- うれしいです – I am happy.
- さむいです – It is cold.
na-adjectives / nouns: [adjective / noun] + だ / です
- 元気だ / 元気です – (is) healthy / energetic
- 静かだ / 静かです – (is) quiet

You never attach だ directly to an i-adjective stem in the present tense:

✗ うれしいだ – incorrect
✓ うれしいです – polite
✓ うれしい – plain / casual

So うれしいです is simply the polite form of the i-adjective うれしい.

Can I just say うれしい without です?

Yes.

うれしいです。 – polite
うれしい。 – plain / casual

In a casual conversation with friends or family, 友達からメッセージをもらうと、とてもうれしい。 is very natural.

Adding です makes the sentence polite, which suits conversations with people you’re not close to, in class, or in writing that aims for standard politeness.

Does 友達 here mean “a friend” or “friends”? How do we know singular vs plural?

Japanese nouns usually do not mark singular or plural unless you add a special ending (like 〜たち) or the context forces a specific reading.

So 友達 can mean:

a friend
the friend
friends
my friends
etc.

In this sentence, both:

“When I get a message from a friend…”
“When I get a message from friends…”

are possible English translations. The Japanese simply says 友達から, and the exact number/person is left to context.

If you really want to emphasize plural, you might say:

友達たちから – but this is not very common and can sound odd/childish in many contexts. Usually, you just keep 友達 and let context handle it.

Why is メッセージ written in katakana?

メッセージ is a loanword from English (message).

In modern Japanese:

Most words borrowed from foreign languages (other than Chinese) are written in katakana.
Examples:
- テレビ (television)
- コンピューター (computer)
- メール (mail / email)
- メッセージ (message)

So メッセージ is in katakana simply because it is a foreign-origin word; this is the standard spelling.