Learn Hardcore Japanese: tomodati to nihongo de hanasu to, aite no kangaekata wo sukosi rikaisuruno ha omosiroi desu. - When I talk in Japanese with a friend, it is interesting to understand a bit of the other person’s way of thinking.

In 友達と, と means “with” (the comitative use):
- 友達と話す = to talk *with a friend*.
In 話すと, と is the conditional “when/if”:
- 話すと、〜 = when (I) talk / if (I) talk, then 〜.

So:

友達と → “with a friend”
話すと → “when I speak / if I speak”

Same particle, but different grammatical roles in each place.

Why is it 日本語で話す and not 日本語を話す?

Both are grammatically correct, but the nuance and typical usage differ:

日本語で話す
- で marks the means / method: to talk *in Japanese / using Japanese*.
- Focus: the act of having a conversation, with Japanese as the medium.
- Very natural when you’re talking about conversations with someone.
日本語を話す
- を marks 日本語 as the direct object: to speak Japanese (as a language).
- Focus: your ability to speak Japanese, or the fact that you speak that language.
- Common in sentences like 日本語を話せます (I can speak Japanese).

In this sentence, we are talking about the situation when I talk in Japanese with my friend, so 日本語で話す is more appropriate.

What exactly does the と after 話す mean in 話すと?

Here と is the conditional “when/if”.

話すと、〜 often translates as “when (I) talk, 〜” or “if (I) talk, 〜”.
It describes a general, regular result: whenever this happens, that tends to follow.

So:

友達と日本語で話すと、〜
→ When I speak in Japanese with my friend, 〜
→ If I speak in Japanese with my friend, (then) 〜.

It is not “and” here; it’s a condition leading to a result.

What does 相手 mean here? Why use 相手 instead of just repeating 友達?

相手 (あいて) literally means “the other party / the person you’re dealing with”.
In conversation, it naturally means “the other person in the conversation”, “your interlocutor”.

Using 相手 instead of repeating 友達:

Makes the sentence more general: not only one specific friend, but whoever you’re talking with.
Emphasizes the role “the other side” rather than their identity as friend.

So it feels like:
When I speak in Japanese with a friend, it’s interesting to understand a bit of the *other person’s way of thinking.
That *other person is your 相手.

Why is it 考え方 and not just 考え? What is the difference?

Both are related to thinking, but they are not the same:

考え (かんがえ)
- “Thought”, “idea”, “opinion” – often about a specific issue.
- Example: その考えは面白いですね。
  That idea/thought is interesting.
考え方 (かんがえかた)
- Literally “way of thinking” (考え + 方 “way/manner”).
- Refers to someone’s general mindset, approach, or perspective.
- Example: 日本人の考え方
  the Japanese way of thinking.

In this sentence, 相手の考え方 means “the other person’s way of thinking / their general perspective”, not just one individual idea.

What does 少し modify in this sentence? Is it “understand a little” or “a small part of their way of thinking”?

Grammatically, 少し modifies 理解する:

少し理解する = to understand a little.

In context:

相手の考え方を少し理解する
= to understand the other person’s way of thinking *a little (bit).*

Semantically, that can be felt both as:

To understand *a small part of their way of thinking, *and
To understand their way of thinking, but only to a small degree.

Both readings point to: not fully, just a bit.

What is the role of の in 理解するのは? Why not just 理解するは?

You cannot say 理解するは. The verb phrase has to be nominalized (turned into a noun-like unit) before it can take は as topic.

That’s what の is doing:

理解する = (to) understand
理解するの = the act of understanding / understanding (it)
理解するのは = as for understanding (it), …

So:

相手の考え方を少し理解するのは面白いです。
Literally: As for (my) understanding the other person’s way of thinking a little, it is interesting.

You could also use こと:

理解することは面白いです。

Both 〜のは and 〜ことは are correct here. の is slightly more colloquial / natural in everyday speech; こと can feel a bit more formal or written.

Why is the word order 相手の考え方を少し理解するのは面白いです and not like English word order?

Japanese is basically SOV (Subject–Object–Verb), while English is SVO.

English: Subject – Verb – Object – Complement
→ It is interesting to understand a little of the other person’s way of thinking.
Japanese structure here:
1. [相手の考え方を少し理解する] の – a whole clause, turned into a noun by の
2. は – topic marker
3. 面白いです – predicate (is interesting)

So the structure is:

(As for) [understanding the other person’s way of thinking a little], (it) is interesting.

Japanese often puts:

Topic (with は) →
Comment/predicate at the end (here, 面白いです).

Why is it 面白いです here? How is 面白い different from 楽しい or 興味深い?

All can be related to “interesting / enjoyable”, but with different nuances:

面白い (おもしろい)
- Broad: interesting, amusing, engaging.
- Used for things that catch your interest or are mentally stimulating (and often enjoyable).
- Very common and natural here.
楽しい (たのしい)
- Fun, enjoyable, pleasant (emotionally, in the moment).
- Focuses more on the feeling “this activity is fun!”.
- 友達と話すのは楽しいです。 = Talking with my friends is fun.
興味深い (きょうみぶかい)
- Literally “deep in interest” → very interesting, intriguing.
- More formal / written and less casual than 面白い.

In this sentence, the speaker likely means:

It is (mentally) interesting / fascinating to understand a bit of their way of thinking → 面白いです fits well.

Where is the subject “I” in this sentence? Why isn’t 私 used?

Japanese often omits the subject when it’s clear from context.

In English, you must say I: When I talk with my friend in Japanese…
In Japanese, if it’s understood that we are talking about your own experience, 私 is usually left out.

If you really want to make it explicit, you can say:

私は友達と日本語で話すと、相手の考え方を少し理解するのは面白いです。

But in normal conversation, 私は would sound a bit heavy or unnecessary unless you are contrasting with someone else.

Could I say 友達に日本語で話す instead of 友達と日本語で話す?

You can say 友達に話す, but the nuance is a bit different:

友達と話す
- と = “with” → to talk with a friend (a mutual conversation).
友達に話す
- に = “to” → to talk to a friend (one-directional: you speaking to them).

In everyday talk about having a conversation together, 友達と話す is more natural.
Here, the idea is a mutual conversation where you discover your partner’s way of thinking, so 友達と is the better choice.