Why 予期せぬ is more common than 予期しない?


予期{よき}する (to expect) is a nominal verb with two negative forms: 予期せぬ and
予期しない. Why the せぬ form is more common than the more familiar しない?




That's simply because It's a _fixed expression_ originated from classical
Japanese.

We have a number of such expressions. See: [Nuance and conversational use of
なきにしもあらず](https://japanese.stackexchange.com/q/42718/5010)




That's simply because It's a _fixed expression_ originated from classical
Japanese.

We have a number of such expressions. See: [Nuance and conversational use of
なきにしもあらず](https://japanese.stackexchange.com/q/42718/5010)

