What is Japanese word for the grammar term "verb base"?

In English language descriptions of the Japanese language verb conjugation for "kau' for example, "ka" is listed as the stem. Base #1 is "wa" to which nai can be added to make ka+wa+nai = kawanai. Base #2 is "i" to which masu can be added to make ka+i+masu = kaimasu. Each base adds a hiragana ending in the sound of "a" for base #1, "i" for base #2, "u" for base #3, "e" for base #4, or "ou" for base #5. My question is; is there a Japanese word for this English term "base". 語幹 (gokan) has been suggested, but I think that refers to the English term "stem", the unchanging part of the verb, in the above system.

Kotae ga areba kanshin shimasu.

  • I'm currently trying to do some research as to why the base system exists/who invented it. What's funny is I can't easily get to the bottom of it. I have a name of a Japanese person that someone wrote on an archiced webite from 2004 but looked up her name and superfically cannot find her name connected to the base system. If I had I might have found out the Japanese name for base that you are looking for. Maybe this means it really was invented by an English native looking to help others to learn Japanese easier. I don't know. More research is needed.
    – user14284
    Commented Apr 27, 2016 at 18:09

2 Answers 2


What you are looking for is probably the word "活用語尾" (Katsuyou Gobi).

That means the changing part that attaches to "語幹" (Gokan).

Check this page (written in Japanese) for the detail description and more examples.

  • Thank you. We're on the right track but what I'm looking for goes between the goken and the katsuyougobi. for example in the verb "kau" the "ka" is the goken. To make a negative you add "wa" to the "ka" making kawa", then you add the "nai". That "wa" is called "base 1" in English but I don't know if it even has a name in Japanese or if it's an English speaking Japanese language teacher's construct. Commented Nov 30, 2015 at 3:22
  • @1bankyoushi I think we usually refer to "wa" in "kawanai" as 未然形活用語尾, "i" in "kaimasu" as 連用形活用語尾...
    – chocolate
    Commented Apr 28, 2016 at 6:06

This page highlights in red the part right after the "語幹" (gokan) and calls it "活用語尾" (katsuyou gobi), so I think it is the term you are looking for.

This page only describes names two parts of the verb: "語幹" (gokan) and "活用語尾" (katsuyou gobi), and then all of the different verb forms.

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