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.
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