1. Absolutely necessary; essential.
2. Obligatory; unavoidable: the routine but indispensable ceremonies of state.
One that is indispensable.
in′dis·pens′a·bili·ty, in′dis·pensa·ble·ness n.
Synonyms: indispensable, critical, essential, necessary, requisite
These adjectives apply to something that cannot be dispensed with: foods that are indispensable to good nutrition; education that is critical to success; funds essential to completing the project; the necessary tools for the job; lacking the requisite qualifications for the position.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.