Indispensable
Indispensable , adjective
[Prefix in- not + dispensable: compare French indispensable.]
1.
Not dispensable; impossible to be omitted, remitted, or spared; absolutely necessary or requisite.
2.
(Ecclesiastical) Not admitting dispensation; not subject to release or exemption. [Rare]
The law was moral and indispensable.
3.
Unavoidable; inevitable. [Obsolete] — Fuller