They both translate to agreement, but I can't quite figure out what the difference is. Based on the answer here, 合意 implies that there was some effort from both parties (e.g., negotiation, compromise) for an agreement to take place, but 同意 doesn't give that nuance.

Also, how did 合 and 同 contribute to the meaning of these 熟語? 同 means same, so it makes sense, but understanding 合 is a bit hard. Is it closer to 合う or to 合わせる?

  • The body of your question appears to answer your title's question. As to whether it's closer to 合う or 合わせる, that question confuses me, because they are different conjugations of the same verb. 合う's basic meaning is to fit, match, or unite with something else. 合わせる is the -aseru (causative) form of 合う, and means to cause something(s) to fit or match, or unite things together. I'm surprised you find it hard to see how the character contributes its meaning, as I would think it would be easier to see than 同, if anything. Commented Jun 5, 2020 at 22:01
  • See guidetojapanese.org/learn/grammar/causepass#Causative_Verbs for more on the relationship between 合う and 合わせる Commented Jun 5, 2020 at 22:03
  • That's interesting, 同 is more apparent to me. (Well, I guess it depends on the person.) Anyway, I wasn't referring to the causative form of 合う which is 合わせる but the transitive verb 合わせる which has the causative 合わせさせる.
    – rebuuilt
    Commented Jun 5, 2020 at 22:49
  • I asked which verb it is closest to because usually kanji compounds can be expressed as a phrase like for example 同じ意見 = 同意
    – rebuuilt
    Commented Jun 5, 2020 at 22:52
  • Causitive form is just a way of "transitive"-izing an intransitive verb. I don't believe that 合わせさせる is a sensible word - what would it even mean? "to cause to cause to match"? I would argue that 合わす is a better candidate for "the transitive of 合う", but you can also still argue that 合わす is the "old abbreviated form" of the causitive. Commented Jun 5, 2020 at 23:04

1 Answer 1


You pretty much answered it on your own, but let me spell it out for completness sake:

The easiest way to put it is probably the difference between "coming to an agreement" and "being in agreement".

合意 is made up of 合う (match, meet) and 意 (opinion) which implies that there was some effort put into making opinions match that were originally different. If I tell my friend that chocolate is the best ice cream flavour and they argue that strawberry tastes better, and after some discussion we agree that both taste great, we have come to an agreement (合意).

同意 on the other hand literally means "same(同) opinion(意)". If I tell my frined that choclate is the best ice cream flavour and they are like "Yes, totally", we are in agreement (同意).

If you make an argument, I might tell you "I agree" either because you have convinced me (合意する) or because I was thinking the same thing (同意する)

Both can be translated to "Agreeing, Agreement" but they give more insight in how that agreement was reached.

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