1. The material or substance on which an enzyme acts.
2. Biology A surface on which an organism grows or is attached.
3. An underlying layer; a substratum.
4. Linguistics An indigenous language that contributes features to the language of an invading people who impose their language on the indigenous population.
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.