1. Not subject to death: immortal deities; the immortal soul.
2. Never to be forgotten; everlasting: immortal words.
3. Of or relating to immortality.
4. Biology Capable of indefinite growth or division. Used of cells in culture.
1. One not subject to death.
2. One whose fame is enduring.
[Middle English, from Old French immortel, from Latin immortālis; see mer- in the Appendix of Indo-European roots.]
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.