わける vs 振り分ける -- What is the ふり doing here?


Consider the following example:

> divide the main folder into sub folders (in case of mail)
>
> フォルダを振り分ける  
>  フォルダをわける

What I want to know is why do we add "ふり"? Why can't we just use "フォルダをわけて"?




分ける just means dividing one thing (or several things) into two or more pieces
(or groups). 振り分ける means sorting or distributing _many_ things into subgroups,
and it is used especially when items arrive over time, as in e-mail filters or
HTTP load balancers. In your case, there is only one main folder but there are
many mails in it, so you can say メール **を** (サブ)フォルダ **に** 振り分ける or フォルダ **を**
2つのサブフォルダ **に** 分ける. フォルダ **を** 振り分ける doesn't look correct to me because it
sounds like there are dozens of random folders to sort.

Regarding this 振る, it means something like "to assign" here. See the third
definition [here](https://dictionary.goo.ne.jp/jn/195909/meaning/m0u/).




分ける just means dividing one thing (or several things) into two or more pieces
(or groups). 振り分ける means sorting or distributing _many_ things into subgroups,
and it is used especially when items arrive over time, as in e-mail filters or
HTTP load balancers. In your case, there is only one main folder but there are
many mails in it, so you can say メール **を** (サブ)フォルダ **に** 振り分ける or フォルダ **を**
2つのサブフォルダ **に** 分ける. フォルダ **を** 振り分ける doesn't look correct to me because it
sounds like there are dozens of random folders to sort.

Regarding this 振る, it means something like "to assign" here. See the third
definition [here](https://dictionary.goo.ne.jp/jn/195909/meaning/m0u/).

