At a glance
Noun はいざ知らず means "X is one thing (it might be understandable for X), but Y...". The part after it is usually surprising, critical, or clearly different from X. It is formal and mostly written.
[Noun] は いざ知らず、[statement about Y]
[Noun] なら いざ知らず、[statement about Y]
初心者はいざ知らず、プロがこんなミスをするとは。 A beginner is one thing, but for a professional to make a mistake like this!
How to form it
| Attaches to | Form | Example |
|---|---|---|
| Noun | Noun + は + いざ知らず、～ | 昔はいざ知らず、～ |
| Noun | Noun + なら + いざ知らず、～ | 子供ならいざ知らず、～ |
| Verb (plain form) | Verb + ならいざ知らず、～ | 知らなかったならいざ知らず、～ |
Register: formal, mostly written or used in speeches. A clause about the contrasting item must follow.