indispensable
1. [ adjective ] not to be dispensed with; essential
Examples:

"foods indispensable to good nutrition"

Related terms: dispensable critical necessary dispensability
2. [ adjective ] absolutely necessary; vitally necessary
Synonyms: essential
Examples:

"essential tools and materials" "funds essential to the completion of the project" "an indispensable worker"

Related terms: necessary
3. [ adjective ] unavoidable
Examples:

"the routine but indispensable ceremonies of state"

Related terms: obligatory
Similar spelling:   indisputable
  indispensability
  indigenous
  in_dispute
  indissoluble