how did 二段 verbs shift into 一段?


How was the process? i know that in 鎌倉時代, the 終止形 and 連体形 started to be used
interchangeably + only the 連体形 form survived and replaced the 終止形.

But here is where i get lost, lets say the classical 下二段 verb **捨つ** , its 連体形
is 捨 **つ** る, which also replaced 終止形 later on, but then it changed to todays
捨 **て** る??

How did that happen?




No.2 from [this answer](https://oshiete.goo.ne.jp/qa/8623094.html) seems the
standard one. I'm just copying from there.

> (1) け け く くる くれ けよ 「受く」（下二段活用）
>
> (2) け け くる くる くれ けよ （中間の時期）
>
> (3) け け ける ける けれ けよ 「受ける」（下一段活用）

So what you are missing is that there was a transition period.

  * (1) -> (2): this is the 終止形と連体形の合流
  * (2) -> (3): this is by analogy. The conjugation that appears most often is 連用形 (the second from left). Thus く changed to け.
  * The transition happened over the long period of time, up to the Edo era.

Probably the transition to ichidan is complete only after modern
standardization (Meiji to early 20th century?).




No.2 from [this answer](https://oshiete.goo.ne.jp/qa/8623094.html) seems the
standard one. I'm just copying from there.

> (1) け け く くる くれ けよ 「受く」（下二段活用）
>
> (2) け け くる くる くれ けよ （中間の時期）
>
> (3) け け ける ける けれ けよ 「受ける」（下一段活用）

So what you are missing is that there was a transition period.

  * (1) -> (2): this is the 終止形と連体形の合流
  * (2) -> (3): this is by analogy. The conjugation that appears most often is 連用形 (the second from left). Thus く changed to け.
  * The transition happened over the long period of time, up to the Edo era.

Probably the transition to ichidan is complete only after modern
standardization (Meiji to early 20th century?).

