Why is 一段 called the 一段?


It's said that 一段 are called 一段 because they keep their stem, but is that
really true?

Like, in 終止形, the verb has る, which is ウ段. And then, in 命令形, it has ろ, which
is オ段.

How do you explain this?




> Its said that 一段 are called 一段 because they keep their stem.

You just answered your own question. 一段 verbs keep their stems intact, while
the suffix change to reflect different conjugations. For example:

  * 食べる dictionary form
  * 食べます respectful form
  * 食べない negative form
  * 食べません negative-respectful form
  * 食べた past tense
  * 食べれば if-form
  * 食べろ imperative form
  * 食べさせる causative form
  * 食べられない negative-potential form
  * The list goes on and on...

You can see how in each of these forms the stem 食べ never changes. Different
endings are added, which happen to include る for dictionary form and ろ for
imperative. For 五段, let's see a comparison:

  * 歩 **く** dictionary form
  * 歩 **き** ます respectful form
  * 歩 **か** ない negative form
  * 歩 **き** ません negative-respectful form
  * 歩 **いた** past tense
  * 歩 **け** ば if-form
  * 歩 **け** imperative form
  * 歩 **か** せる causative form
  * 歩 **け** ない negative-potential form
  * The list goes on and on...

While the stem itself is 歩き, the き could change to か き く け or こ depending on
which 段 the conjugation needs to be in. There are five in total(かきくけこ) hence
the name 五段 verbs.




> Its said that 一段 are called 一段 because they keep their stem.

You just answered your own question. 一段 verbs keep their stems intact, while
the suffix change to reflect different conjugations. For example:

  * 食べる dictionary form
  * 食べます respectful form
  * 食べない negative form
  * 食べません negative-respectful form
  * 食べた past tense
  * 食べれば if-form
  * 食べろ imperative form
  * 食べさせる causative form
  * 食べられない negative-potential form
  * The list goes on and on...

You can see how in each of these forms the stem 食べ never changes. Different
endings are added, which happen to include る for dictionary form and ろ for
imperative. For 五段, let's see a comparison:

  * 歩 **く** dictionary form
  * 歩 **き** ます respectful form
  * 歩 **か** ない negative form
  * 歩 **き** ません negative-respectful form
  * 歩 **いた** past tense
  * 歩 **け** ば if-form
  * 歩 **け** imperative form
  * 歩 **か** せる causative form
  * 歩 **け** ない negative-potential form
  * The list goes on and on...

While the stem itself is 歩き, the き could change to か き く け or こ depending on
which 段 the conjugation needs to be in. There are five in total(かきくけこ) hence
the name 五段 verbs.

