also: でないと
expression
if not; without; otherwise; or else
Conditional expression meaning 'if it is not the case' or 'unless'. Used to state a necessary condition or a negative alternative. Often appears at the beginning of a clause.
急がなければならない。でなければ遅刻する。
We have to hurry. Otherwise we'll be late.
雨でなければ、ピクニックに行きます。
If it doesn't rain, we'll go on a picnic.