According to Wikipedia,

Historical and modern linguists classify Korean as a language isolate. [A language isolate, in the absolute sense, is a natural language with no demonstrable genealogical ... relationship with other languages]

Yet whenever I hear Korean spoken, my ear is tricked for a short time into turning on "Japanese mode"; there are resemblances to Japanese in vocal cadence, pitch variation, syllable enunciation, morae timing, etc. Then I start wondering why I'm not understanding a single word, until I realize I'm not hearing Japanese at all.

The first time this happened to me I was at a hotel in Los Angeles and was flipping through channels on the TV. I was much newer to Japanese at that point and thought I simply didn't have enough practice to understand any rapid speech at all. I watched for about a minute, puzzled, until the screen showed an American speaking English together with some subtitles in Hangul, and I realized this was a Korean show.

Are the two languages actually related in some unrecognized way? Or am I perhaps the only one whose brain initially tries to run Korean through a Japanese filter?

  • That claim from Wiki that Korean is a language isolate is not undisputed. On the other hand, a lot of Americans (or European language speakers(English, Spanish, French, etc.)) can't tell Vietnamese, Thai, or Chinese apart.
    – Eddie Kal
    Commented Feb 28, 2021 at 16:07
  • @EddieKal: This never occurs for me when I hear Mandarin, Cantonese, Tagalog, or Vietnamese.
    – Robusto
    Commented Feb 28, 2021 at 16:19
  • Welcome back! =)
    – Earthliŋ
    Commented Mar 1, 2021 at 15:17

3 Answers 3


I'm a native Japanese speaker, and I have experienced this, too. Depending on the weather condition, it's possible to listen to Korean AM radio in Japan. When the noise is very strong, I sometimes find it difficult to distinguish whether it's in Japanese or in Korean.

I guess this is mainly because of the intonation rather than actual vocabulary. I feel the two languages have similar rhythms when spoken, and they are both relatively "flat" in terms of intonation. (This is my personal experience, and I have no idea if it's academically correct or if it's a coincidence.) On the other hand, the 'four tones' in Chinese sound very distinct to my ears.

In addition, the two languages do share many words of the same Chinese or English roots, and the pronunciations of such words are similar. For example, compare the pronunciation of 大学生 and 대학생 ("university student"). On the other hand, native vocabularies are completely different (eg vs 고양이 for "cat"), and I think this is why they are unrelated in the linguistic sense.

EDIT: Both languages are surprisingly similar in terms of grammar, too. Machine translation works much better between Japanese and Korean than between Japanese and Chinese/English/etc. I don't know why, and apparently linguists don't know much about the reason, either. I found this Wikipedia article: Comparison of Japanese and Korean

  • 1
    Kids these days seem to say ファイティン more than ファイト. A relay loanword: English->Korean->Japanese.
    – Eddie Kal
    Commented Mar 1, 2021 at 4:20
  • 1
    Thank you. At least now I have some evidence I'm not crazy. Well, at least not for this. ^_^
    – Robusto
    Commented Mar 1, 2021 at 14:42
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    Vovin argues that Japanese and Korean are only similar due to being in the same region for an extended period of time and cross-influencing each other. However, grammar is extremely resistant to this kind of influence -- grammatical features are more likely to erode and simplify, than to converge. Also, if regional proximity were the only reason for JA↔KO similarly, then why isn't Korean much more like Chinese? I suspect these languages are like distant cousins, where the genealogy has been forgotten over time. Commented Mar 1, 2021 at 23:34

I am going to attempt an answer from a linguistic angle. It is true that the Korean language and the Japanese language are regarded as two language isolates by many scholars. But efforts to bring them together have not stopped.

You may have heard the term Altaic languages. As one of the early and most hopeful attempts to bring Japanese and Korean together under the rubric of a large overarching language family called the Altaic family. The existence of this umbrella language family is not universally accepted, but since you apparently want something that shows the opposite side of the proclamation that "Japanese and Korean are language isolates", I am going to do just that with arguments that connect these two languages.

Such works as Roy Miller's seminal 1971 book Japanese and the Other Altaic Languages Chicago: University of Chicago Press and Nicholas Poppe's 1965 book Introduction to Altaic Linguistics argue that Japanese-Ryukyuan and Korean are the fourth and fifth branches of Altaic.

One paper I have found that presents a highly cogent argument for viewing Korean and Japanese in the same light is IGARASHI Yuko, 2003, Japanese as an Altaic language: An investigation of Japanese genetic affiliation through biological findings . Some passages from that paper:

In order to determine whether two or more languages are genetically related, the following aspects are generally examined: 1) whether languages have in common a large number of basic vocabulary items and morphological components through regular phonetic correspondences, and 2) whether there are many examples of identical semantics in lexical comparisons.

She argues Korean and Japanese share similar agglutination patterns. She gives three examples: Korean, modern Japanese, old Japanese, all romanized, so I won't attempt a reconstruction of the examples in my answer.

According to Poppe (1965), the agglutination of Altaic word inflection is characterized by adding suffixes mechanically to the stem, and each suffix has a single function. Both Korean and Japanese show this pattern.

She also argues Korean and Japanese have similar postpositions that are characteristic of Altaic languages. She then goes on to claim:

Martin (1991) describes the syntactic similarity between the two languages as follows:

The syntax is a model example of the object-verb language, with modifier preceding modified, with the predicate at the end, and with the relationship between the adjuncts (the noun phrases) and the predicate shown by postpositional particles, by ellipted postpositions, or (as with adverbs) left unmarked (p. 281).


The examples above demonstrate that it is possible to translate word-to-word and morpheme-to-morpheme between Japanese and Korean. Therefore, Japanese syntax is remarkably similar to that of Korean.

  • I have heard of the theory that Japanese, Hungarian, and Finnish are all branches of Uro-Altaic, but I'm not qualified to render any opinion on that.
    – Robusto
    Commented Dec 6, 2023 at 1:33

Genetic relation between languages is usually measured by finding regular correspondences between the two - for example, Fs in native English words like 'father' usually have P in their Latin counterparts like 'pater'. As far as I know, no such regular correspondences between Japanese and Korean have been found. This does not necessarily mean they're unrelated, but if they are related, they split so long ago that it is now impossible to determine.

Genetic relation is also not the only cause of similarity between languages. Geographic proximity often results in languages exerting influence on one another - this sort of thing is called a Sprachbund, I believe - and both languages have a history of borrowing from Chinese, explaining why they might have a lot of similar words.

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    It's not the similarity of words; I don't know any Korean at all. It's just the similarity of the gestalt of the spoken language that makes my ear want to interpret the Korean stream of sounds as Japanese.
    – Robusto
    Commented Feb 28, 2021 at 16:40
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    @Robusto from my experience, it is very rare for Japanese and Korean to sound even slightly similar. When it happens it is probably because of similar words, but Korean overall sound is very distinct to me, same for Chinese. But I have caught myself mistaking Vietnamese for Chinese before. Commented Feb 28, 2021 at 19:49
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    @Felipe: Maybe my brain is defective or my ears more (or overly) sensitive, but I hear similarities, certainly more than slight ones. Which I don't hear in other Asian languages, as noted in my comment above. It has nothing to do with meaning, but with vocal cadence, etc., as noted in my question.
    – Robusto
    Commented Feb 28, 2021 at 20:37
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    I still mishear Korean as Japanese occasionally. In fact the better my Japanese gets the more I can 空耳 various things as Japanese lol. I agree their sounds are similar, and in fact Korean is one of the few source languages that allows for rapid acquisition of Japanese as a second language (pretty high fluency is achievable within 6 months, rivaling or surpassing many English-natives that have been learning for a decade) — there are many reasons for this but similar cadence and phonology certainly helps. Commented Feb 28, 2021 at 23:38
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    I have met dozens of Korean native speakers with amazing Japanese, many of whom had only been studying for a short period of time (a few years at most). It is extremely, extremely rare to ever meet an English native at native-level JP proficiency (especially when it comes to pronunciation/pitch accent/cadence). Just open VRChat for a while on a JP world and you’ll meet a bunch of the Korean natives. Commented Mar 1, 2021 at 20:24

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