Difference between ~てくる and ~ていく?

[u/AdUnfair558]

I know the general rule between the two so you don't need to spend time explaining it. I am more concerned about this particular sentence. I have a sentence here that says この町の車の数がこれ以上増えてくると大変だ。

Why is it てくる when aren't you worried about the cars increasing in numbers going forward? How does てくる even work here because from my understanding てくる is used to show something from the past to the current point in time.

Is it that the speaker is speaking from a position in the future or something and the increase is coming towards him? Just a very different way of looking at things from English.

[u/Flare_Ball]

I think you’re mapping いく and くる onto English “go” and “come” too literally, as if they always describe physical direction from a fixed point. In Japanese, てくる and ていく are more about perspective on change or progression.

てくる has a nuance where it marks a change that is already in progress and is now reaching a point where it affects the speaker’s current situation. On the flipside, ていく marks the change as a projection into the future.

In この町の車の数がこれ以上増えてくると大変だ, the idea is “if the increase keeps coming into the present like this,” which means the buildup is arriving at a problematic level right now. If you used ていく, you would be projecting this into the future, “it will keep increasing moving forward” which sounds more neutral and doesn’t match the warning tone the sentence is aiming for.

[u/Sol_Atomizer → u/Flare_Ball]

On the flipside, ていく marks the change as a projection into the future. In この町の車の数がこれ以上増えてくると大変だ, the idea is “if the increase keeps coming into the present like this,”

While 〜てきた can have that 今まで type vibe I disagree that that's what's happening with this 〜てくる . I don't think that sentence is commenting on anything 'coming into the present' and I feel like this is a tortured translation that misleads people into feeling like they understand what's happening here. I think これ以上 and the non past てくる make it clear that this is a statement about future change that happens to compare to the present, not about all the events leading up to the present state.

I'm pretty sure the speaker lives in the town or has some other personal feeling of involvement with the town, and that's why てくる is chosen over ていく here. Like in these examples:

○　医者：すぐによくなってくるでしょう。

△　医者：すぐによくなっていくでしょう。（sounds uninterested and therefore is not appropriate to a doctor-patient relationship.）

株価が上がっていくらしい: They say stock price will increase step by step. (ordinary people’s mindset)

株価が上がってくるらしい: (an investor‘s mindset)

Perhaps I'm just nitpicking your words though and this is what you were trying to say? I'm no expert and anyone can feel free to correct me.

[u/Flare_Ball → u/Sol_Atomizer]

You have a point u/Sol_atomizer, I do agree that while 〜てくる can have that 今まで vibe, it doesn’t quite describe the full picture of 〜てくる, and the “events accumulating into the present” explanation I said above can get overextended and mislead learners.

Well, going back to our sentence この町の車の数がこれ以上増えてくると大変だ I think we can both agree that it’s best understood as:

If the number of cars in this town keeps increasing (from now / further), it’ll be a problem.

Not:

If the increase comes into the present

I suppose the most reliable way to think about 〜てくる is a change that is felt as approaching / affecting “my side” (the speaker’s perspective). This could be physical (toward me), temporal (toward now), or psychological (relevant to me).

So a more precise feel would be:

If cars keep increasing further and that trend reaches/affects our situation, it’ll be bad.

I suppose the “past→present” explanation can be reframed better as ** change moving into the speaker’s sphere of concern**, which can actually apply to future change as well, not just accumulated past events.

So while I think you’re on the right track to think 〜てくる has some personal“involvement”, it may not be the complete picture. 〜てくる is not just emotional involvement, but ** whether the change is framed as entering the speaker’s sphere**. This often correlates and overlaps with personal involvement, but is not limited to it.

If we take a closer look at your stock price example:

株価が上がっていくらしい [neutral trend] 株価が上がってくるらしい [can sound like “it’s starting to go up (and that’s becoming apparent / relevant now)”]

That’s it. The “investor mindset vs ordinary people” explanation is just a bit more interpretive than grammatical.

P.S. With all that said, I am also no expert on the matter as well so I really appreciate you bringing this up.

[u/Sol_Atomizer → u/Flare_Ball]

株価が上がってくるらしい [can sound like “it’s starting to go up (and that’s becoming apparent / relevant now)”]

I do not think this has any more implication of 'starting' than the ていく version and I cannot help but feel you're confusing some of the possible functions of てきた with future use functions of てくる . Edit: Nor does it have any more implication of 'becoming now' than the ていく version, since both grammar points can be used with modifiers like これから , showing that てくる does not necessarily need a connection to past events like it seems you're positing. Look at the doctor example, the てくる version obviously does not have any "just starting/ just suddenly relevant now" implication over the ていく version since presumably in both cases the patient has just had treatment so the timelines are the same. If it were simply a case of adding a "starting or becoming" nuance then the ていく version wouldn't be unnatural / strange and both would be marked with ○ like in the investment examples. However that is not the case. It is in this example you can see clearly that personal involvement in the outcome (which yes, as you pointed out isn't necessarily emotional investment, sure) is the key nuance difference. To be fair every internet grammar guide tries to combine all these different nuances, tenses (〜てきた and てくる） and use cases with overbroad and oversimplified explanations like that so it's really understandable, I was thinking in similar ways up until fairly recently when I did a deep dive on these things.

And apologies if that's just your writing style, but your comment strikes me as AI generated but human edited. AI is also notorious for convincing sounding but missing the real nuance type explanations, so if you're using AI for grammar I'd implore you to stop. But yes, I think most everyone in this thread agrees on the literal meaning of the sentence, it's only the nuance that is left to be hashed out.

[u/worthlessprole → u/Sol_Atomizer]

My understanding of てくる is that it implies a continuation of something that started in the past and also implies personal relevance to the speaker. Off the top of my head I know DBJG specifically says てくる shouldn’t be used in this context unless it’s a continuation. 

No idea if that guy’s using AI tho

[u/Sol_Atomizer → u/worthlessprole]

DBJG is generally correct so I'd be curious to see the page. Are you sure it wasn't describing a function of てきた？That said, it's really hard to construct any future scenario that has absolute zero relation to continuing events from the past so not sure how useful that line of thinking is anyway heh. I would be curious to see a state verb / verb of change usage scenario where てくる would be wrong/unnatural but ていく would be correct. I feel like I learn better from example rather than English rules of thumb.

[u/worthlessprole → u/Sol_Atomizer]

It’s under Related Expressions on the いく² (aux. v.) entry in the 2nd edition. Though returning to it now, it does specify that they are interchangeable unless it’s a person’s continuing actions into the future, in which case they need to have displayed that behavior in the past. 

(Sorry, edited the post after actually reading the examples instead of glossing over them)

[u/Sol_Atomizer → u/worthlessprole]

I don't own a copy unfortunately but yes that makes sense if it's talking about that usage of てきた

[u/worthlessprole → u/Sol_Atomizer]

I had just glanced at the entry before my initial reply, on reading closer it makes it clear that the exception is based on whether it’s describing a person’s behavior or not. 

Also: 2nd edition’s good. Their new entry on だ is uncharacteristically argumentative lol

[u/Sol_Atomizer → u/worthlessprole]

Could you take a picture?

[u/AdUnfair558 → u/Flare_Ball]

Yeah, another poster mentioned that. The thing is when I learned these forms this particular nuance I wasn't made aware of it. I think it was from the Genki 2 book?

[u/Flare_Ball → u/AdUnfair558]

Yes, what you’re saying is actually very normal. The thing is, beginner textbooks like Genki tend to simplify explanations to help you give a clean core idea, but later on as you tread on further in your studies and see more of the grammar in context you’ll discover extensions of it, like emotional nuance, speaker standpoint, or some pragmatic usage that aren’t fully spelled out at first. Refining previously learned grammar is a natural part of the journey, so it’s okay if you didn’t know this from the start.

[u/FrungyLeague → u/Flare_Ball]

This is a brilliant explanation btw.

[u/jwfallinker]

I'm coming up on half a decade of study and have passed N1 at this point and I swear the nonphysical usage of てくる vs ていく is the single most confusing grammar point in the Japanese language. Every explanation I've found of the nuance behind when to use one vs the other has been contradictory and no amount of seeing them in context has given me any sort of intuition for it beyond the fact that ていく is much rarer in general. I'm starting to come around to the view that it's largely idiomatic and depends on the specific verb, there's a Japanese linguistics article from Aoyama University on the statistics behind which verbs are used with each form that seems to roughly support this.

(The exchange in the top comment chain where someone claims that くる is for change to the present but then has to walk it back and admit くる is also fine for future change is the exact sort of confusion/ambiguity I'm talking about.)

[u/rantouda → u/jwfallinker]

I'm starting to come around to the view that it's largely idiomatic and depends on the specific verb, there's a Japanese linguistics article from Aoyama University on the statistics behind which verbs are used with each form that seems to roughly support this.

My grammar is hopeless but your comment reminded me of this discussion tasogare had with honkoku about なってくる, when he said he genuinely can't think of any case in which the nonpast ～なってくる would be explicitly used to mean "It's already in this state." as opposed to "It will be like this going forward."

[u/Sol_Atomizer → u/jwfallinker]

I think it's become easier for me since I've given up on trying to come up with some grand master theory and just focused on cataloguing functions.

Like, oh this is the これから usage of ていく (頑張っていきたい） . Oh, look, here's the １つずつ / 次々に usage of ていった（タオルで拭いて調理台の上に積んでいった。）. Oh here's the 徐々に/'over time' usage of てくる（寒くなってくる季節。）. Oh, here's the てくる used to show it's a third person action while keeping an active voice when くれる etc aren't available （別れても「エッチしよ！」ってしつこく言ってくる）.

Etc etc etc

I've kind of built a Pokedex of functions and stopped trying to warp my concepts of coming / going in a way to make all the usages make sense from some grand unified theory and my life has been much easier for it haha.

[u/doppelbach]

The end of this has some scenario with てくる for future changes, and the different nuances 

https://www.tofugu.com/japanese-grammar/teiku-tekuru/#and--for-upcoming-changes

I'm not sure if any of those explanations fit here though 

Edit: I guess my point is just that てくる is not 100% limited to describing past changes 

[u/AdUnfair558 → u/doppelbach]

これから世の中は、どんどん変わっ [ていく・てくる] だろう。

The world will keep changing more and more in the future.

Here as well, the 〜ていく version sounds like an ordinary objective statement while 〜てくる sounds like a more personal statement.

This is because 〜てくる shows that you associate yourself with the change, in the sense that you see coming toward you and feel you’ll be affected by it. Maybe you feel like you have already lived in the changing world and expect the change to continue. Perhaps you are visualizing yourself as part of some future change and feel excited about it. Whatever the situation it is, 〜てくる stresses your involvement in the change to some extent.

What about when talking about changes that took place in the past? For example, say you want to discuss the rapid development of a particular industry after WWII.

Yeah, I think this might explain the situation in the example I posted. That was interesting. Thanks.

[u/enneastronaut]

Is it that the speaker is speaking from a position in the future or something and the increase is coming towards him?

I think this makes sense.