How can a verb be intransitive and imperative at the same time?


Like, for example, I understand 折れ but in what case should one use 折れろ?

Also, jisho says the negative imperative is 折るな but what about 折れない？




折れろ is the imperative form of 折れる as an intransitive verb.  
As you know, 折れる is also the potential form of a transitive verb 折る.

The following sentence shows you how 折れろ is used as a verb being intransitive
and imperative at the same time.

  * 犯人{はんにん}はその細｛ほそ｝い枝｛えだ｝にぶら下｛さ｝がった。「 **折｛お｝れろ** 、 **折｛お｝れろ** ！」と見{み｝ている人｛ひと｝は期待｛きたい｝したが、犯人｛はんにん｝はその枝｛えだ｝を伝｛つた｝って塀｛へい｝の向｛む｝こう側｛がわ｝へ逃｛に｝げて行｛い｝った。 _The criminal hung from the thin branch. The crowd shouted "Break! Break!" hoping the branch would break, but the criminal hung along the branch and fled to the other side of the fence._

> what about 折れない？

折れない is the negative form of an intransitive verb 折れる or the negative
potential form of a transitive verb 折る, not the negative imperative form of it
like:

  * **negative intransitive:** この枝{えだ}は **折れない** からブランコを吊{つ}り下{さ}げることができるよ。  
_You can hang a swing because this branch will not break_.

  * **negative potential and transitive:** その枝{えだ}を僕{ぼく}は **折れない** が力{ちから}の強{つよ}い君{きみ}なら折れると思{おも}う。 _I cannot break the branch, but I think that you can, because you are stronger than me_.




**折る** is a **godan transitive** verb ("to break something"). It conjugates
like:

> 折らない, 折ります, 折って, 折れば, 折れ, 折ろう.

**折れる** is an **ichidan intransitive** verb ("to be broken"). It conjugates
like:

> 折れない, 折れます, 折れて, 折れれば, 折れろ, 折れよう.

**折れる** is also the **[potential
form](http://www.guidetojapanese.org/potential.html) of 折る**. It conjugates
like:

> 折れない, 折れます, 折れて, 折れれば

折れろ is perhaps "intransitive and imperative at the same time". It can mean
"Break (by itself)!" or "Give up!"

The negative imperative of 折る is 折るな ("don't break it"), and the negative
imperative of 折れる is 折れるな ("don't break by itself; don't be broken; don't give
up"). 折れるな is a way to say "Don't give up", so it's heard more often than 折れろ.

取る (transitive "to remove something") and 取れる (intransitive "to be removed"
and potential "can remove something") conjugate exactly like these.

