i was playing Katahane last night, in it Light and Wakaba refer to their mother as Kaa-san while Light refers to Wakaba (his older sister) as Nee-san and when meeting with Rien he says for them to call him Jii-san by commenting

If you did not know my name or who i was i would just be an old man to you correct?

^ (he's not saying that in a bad way mind you)

also in Fate/Stay Night, Sakura refers to Rin as Nee-san and the 2 of them are sister however Sakura was adopted out to prevent a potential fight over Magus Succession between them (like what happens with Touko and Aoko)

from my understanding, Okaa-san is Mother, Onee-San is Big Sister and Ojii-san is Grandfather, now while Kaa-san and Nee-san i can still determine refer to Mother and Sister i'm assuming Jii-san is something close to Grandfather as Rein in Katahane is almost like a grandfather to Cero and since Wakaba is close to Cero (potential love interest in one route) i'm assuming he doesn't mind being though of as a grandfather but that's seculation,

so i am wondering, what is the difference between Okaa-san/Onee-san/Ojii-san and Kaa-san/Nee-san/Jii-san apart from the obvious drop of O from each word

  • 3
    @TokyoNagoya: How does knowing the Japanese alphabet help answer the difference between these words?
    – istrasci
    Commented Nov 11, 2013 at 22:20
  • @istrasci ok i think i get it, what i was asking was the difference between the meaning while TokyoNagoya was refing to the obvious drop of O in the words, edited my question for that
    – Memor-X
    Commented Nov 11, 2013 at 22:23
  • 2
    It would be a little easier to understand your questions if they were written in proper English.
    – user1478
    Commented Nov 11, 2013 at 23:34

1 Answer 1


o is an "honorific prefix" (read about honorific speech in Japanese on Wikipedia), which is a more polite way to refer to someone's or your own grandfather/mother/sister/etc.

There is also お父さん otōsan "father", おばあさん obāsan "grandmother" and お兄さん oniisan "big brother", which fit the same pattern.

We have a few questions about お and its "brother" ご on this site, which might be of interest. You'll probably understand the meaning of お from reading these questions alone.

  • (1) I do not think that adding お to 母さん/姉さん/じいさん/etc. affects the formality of the word. (2) I think that writing お父さん as otōsan and おばあさん as obaasan is a mixture of two different romanization conventions. (3) The question mentioned お母さん, お姉さん, and おじいさん, and you mentioned お父さん and おばあさん…. I am afraid that お兄さん is logically missing! Commented Nov 12, 2013 at 1:47
  • 2
    @TsuyoshiIto Maybe formality necessitates politeness, so that "formal" is redundant? (2) Personally, I use ワープロローマ字, but I think in my romanization attempt, I correctly used the convention of traditional Hepburn romanization, but I'll switch to modified Hepburn. (3) Added お兄さん, because you asked for it ;)
    – Earthliŋ
    Commented Nov 12, 2013 at 9:39
  • (1) Thank you for the edit. In response to the comment, though, I still think that “formal” is not redundant but incorrect in the case of the current question. (2) This was my fault. I did not know that there was a convention to use aa for ああ and ō for おう read as おー. My apologies. (3) Thanks! :) Commented Nov 12, 2013 at 10:13
  • I think that Japanese can be formal, polite, both, or neither--that's what my books say, at any rate. (The distinction between formal and polite has always been challenging for me as a learner, to be honest...)
    – user1478
    Commented Nov 12, 2013 at 19:22
  • 1
    @TsuyoshiIto Thinking more about it, I agree that neither 父さん nor お父さん are particularly formal, but quite the opposite. In any formal context "father" would be 父{ちち} or 父親. Curious that a polite and formal version doesn't really exist any longer (unless you want to sound like a warrior and use 父上).
    – Earthliŋ
    Commented Nov 12, 2013 at 22:35

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