ao seems to be used very much interchangeably for both blue and green. Why is that so, and how does 緑 midori play into this?

  • I'm sure I heard somebody saying gairaigo "blue" in the last 2 or 3 days also... Commented Jun 13, 2011 at 12:42
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    @hippietrail: ブルー is definitely used in modern Japanese, but I usually hear it in reference to the emotion rather than the color. Commented Jun 13, 2011 at 12:55
  • @Derek: Ah that could be, it was among volunteers cleaning up Kesennuma/Minami Sanriku and I could by know means follow the rest of what was being said. Commented Jun 13, 2011 at 13:00
  • @hippietrail Otsukaresama! _(_ _)_
    – deceze
    Commented Jun 13, 2011 at 13:05
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    The distinction of blue from yellow-green is one of the last "basic" color terms (one word) to evolve in most languages, according to the seminal studies of Kay and Berlin: See this Wikipedia text and chart for info. You can even see it in English: Apparently, once upon a time in Old English, we did not distinguish between yellow (yellow-greenish) and blue; if you check the etymologies, one finds that they go back to the same PIE root, *bhle-was.
    – Uticensis
    Commented Jun 13, 2011 at 17:50

3 Answers 3


Beside some of the historical examples mentioned by Derek, there is also an inherent nuance that separates 青 from 'blue', as it is commonly understood in Western culture (and similarly, albeit less strongly, for 緑 and 'green'). This is not unique to Japanese-English and probably applicable to any pairs of sufficiently separate cultures: colours are, for a large part, an artificial construct and there is only limited reasons two people should pick the same arbitrary frontier along the green-blue continuum (or red-orange, or yellow-green etc). I recommend digging in Google Scholar for more on that, but it's worth mentioning that there is much debate on what the causes and extent of these differences between cultures are.

Anyway, back to 青/緑: leaving aside the fact that the past 100 years of intermingling with Western culture have no doubt influenced the native Japanese perception of these colours, there is still a real difference between the range of what a Japanese will call 青い and a Westerner call 'blue' (talking about pure colours here, not objects' traditional colours, which might be tied to historical reasons). 'Blue' for 青 and 'green' for 緑 are just approximations (as are probably most other native colour translations).

A diagram might be the easiest way to put it. Assuming that horizontal line represents the true continuum of hues from blue to green, and the vertical bars, the separation between the two colours in Japanese and English respectively, you'd have:

    青い        |  緑
  Blue  |  Green

As a result, when talking about something on the far left (say, the sky) or the far right (say, fresh verdure), both English and Japanese words agree quite well. If you pick things that are in that middle area where the definitions do not match, you get these quizzical looks and people arguing "what do you mean green? it's obviously blue!" etc.

Sorry for the longwinded answer to what is a fairly basic/obvious point... ;-)

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    Don't apologize this is a great answer! Commented Jun 13, 2011 at 23:58
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    For more (completely Japanese-unrelated) musings on the subjectivity of colour perception and naming, I strongly recommend checking this awesome xkcd project that surveyed internet users on how they view colours and analysed their results (unfortunately without nationality information)... particularly the colour naming map, which is a 2D version of what I tried to do above...
    – Dave
    Commented Jun 14, 2011 at 2:45
  • The link to the paper at springerlink.com is broken. I'm also unable to find any copy saved on the Wayback Machine.
    – user51980
    Commented Jul 20, 2022 at 15:00

This page in the 日本語Q&A over at ALC addresses this question. Apparently the historical definition of 青【あお】, even when defined narrowly, covered an entire range of colors which are today separated as 青【あお】, 緑【みどり】, and 藍【あい】 (indigo). This trend carried into the modern language, and many words which refer to things that are actually 緑【みどり】 still use 青【あお】: 青葉【あおば】 and 青竹【あおだけ】 are two examples given on the linked page. (This in spite of the fact that 緑【みどり】 has existed alongside 青【あお】 all this time.)

Apparently when traffic signals came along, 緑信号【みどりしんごう】 was the official name at first, but it was eventually overtaken by 青信号【あおしんごう】 in common use and this latter name became the official term.

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    This actually happens in all languages, it's one of the puzzles of linguistics. They're still trying to figure out how and why Latin colour words were applied. Commented Jun 13, 2011 at 12:57
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    More on color (non-)universality.
    – Kosmonaut
    Commented Jun 13, 2011 at 19:17

This partially also has to do with the fact that in old Japanese they only used four colours: あか・あお・しろ・くろ. Obviously, with this limitation, あお came to represent a wide range of different cool shades. Then once more "colours started to be used", a lot of things retained their original descriptions as あお.

Edit: Here is that handout I have from my Japanese teacher which I describe below in the comment. It is from a book she has, but I don't have the reference for it.


  • 昔の日本では、あか(紅)・あお(緑)・しろ(白)・くろ(黒)の四色 この四色は、「青く[ない]、青かっ[た]、青い[。]、青い[物]、青けれ[ば]...」と活用するように、 「青い・赤い・黒い・白い」といずれも形容詞になります。 それに対して、緑は形容詞として「緑い」とは使えません。 また「青々と」「赤々と」「黒々と」「白々と」のように副詞にできるのに対して、「緑々と」という表現はありません。 このような点から、青・赤・黒・白の四語と緑は、別なのではないかと考えられます。 文献上で「緑」が用いられるのは、平安時代ごろからです。 *注)平安時代:794〜1185 それ以前は、青いが黒から白までの間の広い範囲の色を表したようです。 (特に現代の青・緑・藍の三色を表すことが多かったようです。)
  • 1930年に日本で初めて信号機が設置されたとき、 法令では緑色信号だったのですが、新聞が「青」と掲載してしまったことや、 色の三原色、赤・青・黄にあてはめると理解されやすかったために「青」信号が定着してしまいました。 1947年には法令でも青信号と呼ぶようになりました。 日本語の青を表す範囲は広く、「青りんご」や「青葉」など緑のものも青と呼んでいます。 ちなみに現在の信号機は緑ではなく青緑色で点灯前は青になっているはずです。
  • あお   青・蒼・藍 → 空・顔色・信号・草
    みどり  緑・翠・碧
  • @istrasci: Do you have any sources for this claim? I must admit this sounds a little sketchy... Even if you discount the numerous "○色" compounds (茶色 etc.), which I see no reason to, I am pretty sure you would still have more than 4 colour-defining words in older Japanese. 紫【むらさき】 to pick one at random, is pretty old. The Jp Wikipedia for dyes lists many more, in use since "ancient times"...
    – Dave
    Commented Jun 14, 2011 at 14:45
  • Yes, admittedly it sounds very questionable. The only source I have is a type-up I received from my Japanese teacher. I know she didn't make it up, but I don't know where she got it from. I'll add it later (during my lunch hour) as a comment.
    – istrasci
    Commented Jun 14, 2011 at 15:27
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    Would love to hear more, thanks... At the risk of stirring up some old controversies, I'd recommend taking any statement that starts by "Japan always had/has X of Y, unlike all other cultures" with a huge grain of grain of salt, regardless of what native authority figure utters it. In my personal experience the love of 日本人論 way too often trumps critical sense and fact-checking in these instances...
    – Dave
    Commented Jun 14, 2011 at 16:02
  • +1 for stressing the importance of sources. I very much agree with Dave in this. Personally, I call it the "Cultural Blackhole argument".
    – wallyqs
    Commented Jun 15, 2011 at 0:24
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    @Dave: An alternative analysis is that there are only four (surviving) Yamato words that are only colour words: aka, ao, shiro, kuro. Murasaki originally referred to "wisteria" the plant, as suggested also in the etymology (mura from 群{む}る "to group together", saki from 咲{さ}く "to bloom"). Midori originally referred to new plant buds, and this term likely also has a compound derivation. The other various colour words are (I think) all borrowings from Chinese, such as 黄{き}色{いろ} or 銀{ぎん}, or obvious compounds of native words, such as 狐{きつね}色{いろ} or 鼠{ねずみ}色{いろ}. Commented Jan 17, 2017 at 20:05

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