Indispensable /(?)/

In·dis·pen·sa·ble

Indispensable

a.
  1. Not dispensable; impossible to be omitted, remitted, or spared; absolutely necessary or requisite.
  2. Not admitting dispensation; not subject to release or exemption. (Eccl.) [R.]
    The law was moral and indispensable.
  3. Unavoidable; inevitable. [Obs.]