indispensable indispensable /ˌɪndɪˈspɛnsəbəl/

adjective

1. () Not to be dispensed with; essential  ( indispensable )
   not to be dispensed with; essential
    Foods indispensable to good nutrition
   foods indispensable to good nutrition
   
2. () Absolutely necessary; vitally necessary  ( indispensable , essential )
   absolutely necessary; vitally necessary
    Essential tools and materials
   essential tools and materials
    Funds essential to the completion of the project
   funds essential to the completion of the project
    An indispensable worker
   an indispensable worker
   
3. Unavoidable  ( indispensable )
   unavoidable
    The routine but indispensable ceremonies of state
   the routine but indispensable ceremonies of state