saneseoneun jeoldae honja gaji ma.

산에서는 is 산 + 에서 + 는.

• 산 = mountain
• 에서 = at/in/from a place, depending on context
• 는 = topic/contrast marker

Here, 에서는 gives a sense like in the mountains or when it comes to the mountains. The 는 adds a slight contrastive feeling, as if the speaker is saying, at least in the mountains, never go alone.

If you said 산에 절대 혼자 가지 마, that would more directly sound like don't go to the mountain / mountains alone. The version with 산에서는 feels a bit more like a general safety warning about mountain situations.

It can mean either, depending on context.

Korean often uses a bare singular noun to talk about something in a general sense. So 산에서는 can naturally mean:

• on a mountain
• in the mountains
• when you're in mountain areas

English usually forces you to choose between singular and plural, but Korean often leaves that open unless the context makes it specific.

절대 means absolutely, never, or by no means.

It strongly emphasizes the prohibition. So this is not just don't go alone; it is more like:

• absolutely do not go alone
• never go alone

A useful point: 절대 is very commonly used with negative expressions. So learners will often see patterns like:

• 절대 하지 마 = absolutely don't do it
• 절대 안 돼 = absolutely not

혼자 means alone or by oneself.

In this sentence, it works like an adverb: don't go alone.
So 혼자 가지 마 = don't go by yourself.

혼자서 is very similar. It can sound a little more explicit or slightly more natural in some contexts, but the meaning is basically the same here:

• 혼자 가지 마
• 혼자서 가지 마

Both mean don't go alone.

가지 마 is the casual negative command form of 가다 (to go).

It is made with:

• verb stem + -지 마

So:

• 가다 → stem 가-
• 가 + 지 마 → 가지 마

This pattern is very common:

• 먹다 → 먹지 마 = don't eat
• 보다 → 보지 마 = don't look
• 가다 → 가지 마 = don't go

So -지 마 is the key pattern meaning don't do X.

Because Korean negative commands are not made by simply adding 마 to the verb stem.

The normal pattern is:

• verb stem + 지 마

So with 가다, you must say 가지 마, not 가 마.

You can think of -지 마 as a set grammar pattern meaning don't.

The subject is understood as you.

Korean very often leaves out subjects when they are obvious from context, especially in commands. In English, you usually need to say or at least understand you:

• (You) absolutely don't go alone in the mountains.

In Korean, leaving it out is completely normal.

It is casual and fairly direct.

가지 마 is a plain, informal command, so it is natural when speaking to:

• a friend
• a younger person
• a family member
• someone in an urgent situation

If you want to be more polite, you could say:

• 산에서는 절대 혼자 가지 마세요.

That means the same thing, but in a polite style.

Yes, there is a small difference in nuance.

• 산에 절대 혼자 가지 마 = don't go to the mountain / mountains alone
• 산에서는 절대 혼자 가지 마 = in the mountains, absolutely don't go alone or when it comes to the mountains, don't go alone

So 산에 focuses more directly on the destination, while 산에서는 sets up the mountain context as the topic and can sound more like a general rule or warning.

Yes, Korean word order is flexible, especially with adverbs.

For example, these are all understandable:

• 산에서는 절대 혼자 가지 마
• 산에서는 혼자 절대 가지 마
• 절대 산에서는 혼자 가지 마

But the original order sounds very natural. It flows well as:

1. setting: 산에서는
2. strong emphasis: 절대
3. manner: 혼자
4. command: 가지 마

So even though some movement is possible, the original sentence is a very natural way to say it.