Japanese word “koso” (こそ) explained in detail

By | October 22, 2015

The word “koso” in Japanese, usually written in Hiragana as こそ, isn’t exactly a frequent word in Japanese, nor is it necessary in order to express most things in the language. However, there are a few common usages which are good to learn, regardless of your level, and you may even be able to employ a few of these in your own speech and writing.

Looking up the word in an Japanese->English dictionary gives a few sample sentences, some which are pretty useful, but it doesn’t give any overall meaning, leaving that for your imagination.

If you try to get daring and check out the meaning in the Japanese->Japanese dictionary, you’ll see there are several meanings and quite a bit of explanation to wade through. Fortunately much of that is for uses that are not all that common (or archaic) which the average person doesn’t need to bother with.

Generally, “koso” is used after a noun in order to emphasize it in some way. Saying “emphasize” is a bit vague though, so let’s look at some common phrases with this word in them.

  • こちらこそどうもありがとうございます。  (Kochira koso doumo arigatou gozaimasu)
  • *I* am the one who should be doing the thanking.

Here the word “kochira” stands in for the first person pronoun, and refers to the speaker. The word “koso” is effectively like adding italics to the word “I”, and in English would be expressed via a change of tone on that word.

This expression would typically be used after some one thanks you, and you want to be extra polite and say “No, it is *me* who should be doing the thanking”. Note that this is a very non-literal translation, since the concept of “should” is not explicitly in the Japanese sentence. However it does capture it’s intended meaning pretty accurately.

  • そっちこそ、どう思う? (Socchi koso, dou omou?)
  • So what do *you* think?

This expression is very similar to the previous one, except for that it is informal and the emphasis is on the listener, not the speaker. Here “socchi” is a shortening of “sochira” which refers to the listener, in other words “you”.

You can use this phrase in response to someone asking what you think about a matter, and it essentially means “You tell me first”.

Another common phrase is when you add “koso” after “dakara” (“that is why”) to end up with “dakara koso”. Again, “koso” serves to emphasize the word before it, and in this case it often implies that the reason for something is unexpected, possibly even the opposite of what someone thought.

  • そう、誰しもいつかは死ぬ。だからこそ生きる意味があるんだ。 (Sou, dareshimo itsuka ha shinu. Dakara koso ikiru imi ga aru n da)
  • Yes, everyone will die eventually. That is the very reason that there is meaning to our lives.

The reason “dakara koso” is a perfect fit here is because some people might say “We are all going to die, so life is meaningless”. The speaker is acknowledging that and saying that it’s actually the opposite, it is only because we die that life has meaning.

Besides the above specific usages, you can always just add “koso” after a noun to emphasize it. However, I feel that “koso” has sort of a literary, intellectual connotation to it, so if you go around randomly overusing this word you might get some strange looks. In the right situation the phrase “日本語こそ難しいよ!” (Nihongo koso muzukashii yo) could work, but I think you would rarely hear the word used in such a way in a typical conversation. I have heard the phrase “sore koso” to stand in for an emphasized *that* once in a while, however.

While researching this word to make sure I got my facts straight, I discovered something interesting – the word “youkoso” is actually derived from “yoku koso”, which is a shortening for something like “yoku koso kite kuremashita”. Here, it is said that the “yoku koso” imparts a meaning of thanks with respect to the act of someone arriving. Thats why “youkoso” is often translated as “Welcome”. (You can see a long post about this here, in Japanese).

By the way, the words “kosodate” (子育て, raising a child, “ko + sodate”) and “kosokoso” (being sneaky about something) have no relation to the word “koso” which I discussed here.

Now hopefully next time you come across this word you’ll have some idea what it means.

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5 thoughts on “Japanese word “koso” (こそ) explained in detail

  1. anon

    I was watching a show and someone said 今日こそ契約を取らないと
    and the subtitles stated “I’ve got to make some contracts”
    Does a こそ + a negative word mean something like “must”, or “have to”?

    1. locksleyu Post author

      No, it doesn’t really have a direct connotation of ‘must’ or ‘have to’, though I guess it can have that nuance in certain cases.

      To me it has the connotation of ‘definitely!’ or ‘for sure!’. Like in the phrase “今日こそ勝ってみせる!”

      By the way, in the example you gave, though the verb is negative, it is implying the “〜しないといけない” pattern, which means “has to” or “must”. In other words, “If I don’t XXX, it will be bad!”

  2. Selma

    Hello. I came looking for the meaning of koso that I heard a friend say was good for our health, but was unable to find it. BUT I came across this post and I’m most happy for it. It’s eloquent. Very informative. I enjoyed knowing this. Thank you.
    Kochira koso, Arigatou. The pleasure is all mine. Selma.

  3. Kudsy

    Hi, I overheard someone said watashi koso. Would you give an example of this and the purpose of using it.

    1. locksleyu Post author

      For example, if someone said they were bad at Japanese, you could say, “iie, watashi koso nihongo ga heta desu yo”, which has the nuance of “No, *I* am the one who is bad at Japanese”.

      But it depends on the situation, if you give me more details I can try to help better.


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