1. Serving to define or identify as distinct from others: "The Enlightenment pushed this project further trying to make science and its hallmark method definitive of the rational life" (Peter Machamer).
2. Supplying or being a final settlement or decision; conclusive: "The fall of the city Constantine had founded marked the definitive end of the Christian Eastern Empire" (James Carroll). See Synonyms at decisive.
3. Authoritative and complete: a definitive biography. See Usage Note at definite.
4. Mass produced in indefinite quantities over an indefinite period of time. Used of postage stamps.
5. Biology Fully formed or developed, as an organ or structure.
1. Grammar A word that defines or limits, such as the definite article or a demonstrative pronoun.
2. A definitive postage stamp.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 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.