べからず

べからず is a classical, formal prohibition form meaning strongly 'do not' or 'you must not'. It is often found in written notices, literature, or historical/legal contexts. It sounds archaic or solemn when used in modern speech, and it is best avoided in casual conversation. The accompanying べからざる is the prenominal form used to describe something that is 'undeniable/indispensable' or 'unavoidable' depending on context, but commonly conveys the sense of 'cannot be ~' or 'indisputable ~' as an attributive modifier to a noun.