What are the differences among the following two-kanji words that seem to mean "eternity":

  • 永遠 {えいえん}
  • 永久 {とわ}
  • 永世 {えいせい}
  • 永代 {えいたい}
  • 永劫 {えいごう}
  • 永永 {えいえい}
  • 久遠 {きゅうえん}
  • 悠久 {ゆうきゅう}
  • 恒久 {こうきゅう}
  • 恒常 {こうじょう}
  • 長久 {ちょうきゅう}
  • 無窮 {むきゅう}

Please include any other related words (preferably two-kanji only) but please exclude those that make use of period of a lifetime like 一生, 末代 etc, or big number of years/era like 千代, 万古 etc.

p/s: I noticed that the first two 永遠 and 永久 are the most commonly used; is it true and why them instead of the others?

  • 1
    "永代" seems to fit OK. It appears to be used in some legal terms for "in perpetuity". Also, unless I'm mistaken, although "とわ" is one possible reading for "永久", I think it's normally read "えいきゅう".
    – rdb
    Commented Sep 12, 2011 at 4:15
  • 4
    I'm not sure that explaining the nuances between 12 synonyms is very "fun"…
    – Axioplase
    Commented Sep 12, 2011 at 10:22
  • 2
    @Axioplase: I agree. Those “fun with synonyms” questions asking for comparison among many similar words sound like “synonym hell” to me. Commented Sep 16, 2011 at 17:44
  • 2
    @Lukman, You forgot 永久に can also be read tokoshie ni Commented Sep 24, 2011 at 5:02
  • 2
    @Axioplase, Tsuyoshi -- it seems relative. A topic one enjoys studying may be tedious/work/unenjoyable for another. I personally enjoy studying synonyms.
    – istrasci
    Commented Sep 24, 2011 at 15:41

3 Answers 3


There's a lot of good information in the other answer already, the main goal of this answer is to fill in some of the other definitions etc.

  • 永遠{えいえん}:

    When something continues for all time in a certain state without ending, for example love which never ends or neverending world peace. 永遠に can take the meaning of "forever" or less commonly "permanently". Highly interchangeable with 永久{えいきゅう} and vice-versa.

  • 永久{えいきゅう}: 

    Something which is permanent or perpetual, for example permanent love or a permanent license. Also used for immortal achievements, works, fame etc. 永久に can take the meaning of "permanently" or less commonly "forever".

    Usually えいきゅう, but can also be pronounced えいこう. Is sometimes pronounced とわ to take a more abstract meaning, but the Kanji 常{とわ} is more common with that reading according to Daijirin.

  • 永世{えいせい}:

    A long period of months and years or an era which never ends. Also used in 永世[中立国]{ちゅうりつこく} as Joshua has noted.

  • 永劫{えいごう}:

    An eon. (The other answer has already done a great job explaining about 永劫[回帰]{かいき} I think.)

  • 永代{えいたい}:

    A very long time in months/years or eternity. Used in 永代[供養]{くよう}, "services performed in perpetuity by a Buddhist temple for the repose of a departed soul" according to JMDict.

  • [永々]{えいえい}:

    I think this can mean "forever", but it generally just emphasizes a notably long period of time, e.g. "the practice has continued for 100 years." Usually written with a くりかえし () but can also be written as 永永.

  • 久遠{くおん}:

    A buddhist term for eternity. Infinite time or the distant past/distant future. Usually pronounced くおん but can also be きゅうえん.

  • 悠久{ゆうきゅう}:

    Unending. Used in 悠久の[歴史]{れきし} (neverending history.)

  • 恒久{こうきゅう}:

    Used in permanent government/constitutions/laws/treaties/measures/solutions et al.

  • 恒常{こうじょう}:

    Doesn't really mean "eternal" so much as "constant", e.g. "constant weather".

  • 長久{ちょうきゅう}:

    Used in wars/battles to indicate eternal luck/good fortune e.g. [武運]{ぶうん}長久 and 幸運{こううん}長久. Also indicates the Choukyuu era from 10/11/1040-24/11/1044 as has been noted.

  • 無窮{むきゅう}:

    Something which is always in a state which never changes, e.g. "an unchanging art style" or something which is of the state of being infinite/immortal.

  1. 永遠{えいえん}

    I don't think she'll ever get sick of that guy (her husband).

  2. 永久{えいきゅう}

    I wont forget this.

  3. 永世{えいせい}

    A Neutral Country (in Japanese without the word eisei it is not implied that a country has a policy of neutrality. Whereas, in English, the word Neutral Country by itself implies that this is a policy that the country has singed onto. The eisei portion of this word makes the idea a unchangeable bound policy.)

  4. 永代{えいたい}

    pronounced eidai and this is used as a name of a person or place. There is a city in Tokyo called Eidai and a bridge called Eidai-bashi

  5. 永劫{えいごう}

    An ancient Greek philosophy called "Eternal Recurrence", which is also found in ideas like Reincarnation and the circle of life ideas, where life never dies, it just changes or revolves.

  6. 永永{えいえい}

    "Same old same old" might be a good definition for the idea that there was nothing new that week and every day was kinda the same, unchanging.

  7. 久遠{きゅうえん}

    Pronounced Ku-On and used in people's names

  8. 悠久{ゆうきゅう}

    Sometimes written UQ and found in Game Titles but has the same meaning as Eien 永遠 except used for game or book or movie titles.

  9. 恒久{こうきゅう}

    A world without war is a pipe dream. (in Japanese uninterrupted peace means a world without war)

  10. 恒常{こうじょう}

    The constant border wars between England and Scotland finally came to an end.

  11. 長久{ちょうきゅう}

    The name of the Japanese "Chokyu Era"

  12. 無窮{むきゅう} (see number 6)

  • 1
    How could this answer possibly have gotten voted down O_o Just because I didn't go with a "traditional" "glossed" translation but provided correct nuance and syntax? Commented Sep 24, 2011 at 7:03
  • 2
    1. You just have descriptions about prononounciation for randomly picked ones, which are inconsistent, redundant given your furigana, and further wrong (e.g., 久遠 is not Ku-On if your furigana is right). 2. Particularly for (4, 7, 11), your description is completely irrelevant for the usage in question. 3. Just giving a single example without any explanation does not explain the difference. Especially, the OP already knows that they are all related to eternity. What is asked is the finer difference.
    – user458
    Commented Sep 24, 2011 at 7:21
  • 1
    @sawa, where is my syntax incorrect? All the English sentences flow nicely without error. Did someone have a bad day today? Commented Sep 24, 2011 at 9:16
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    @sawa of you are aware of this "finer" difference why have you not created this utopia answer of yours? It's because you don't know what you're talking about. I think it is up to the person who asked to decide if my answer is sufficient. No one else did the research for each word. Commented Sep 24, 2011 at 9:23
  • 4
    I don't think sawa is saying that 久遠 cannot be pronounced kuon; he's pointing out that you have it as "久遠きゅうえん" in your list, and as "Ku-On" in your explanation. And of all the people on this board, by my lights at least, sawa probably "knows what he's talking about" better than 99% of us.
    – rdb
    Commented Sep 24, 2011 at 10:08

I'd like to add: 無限{むげん}. It means infinity but infinity and eternity can be interchangeable at times..

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