ず

Etymology 2
From. Generally considered to be a combination of negation suffix in its  of  + honorific suffix.

→ * →

Appears both as zu and as the older nisu form in the  poetry anthology.

Suffix

 * 1) not doing

Usage notes
Much as the older negation suffix and the modern negation suffix, ず (zu) must come after the  of a verb.

The suffix ず (zu) is more formal than the everyday negation suffix.