1. A learning process by which a subject develops a consistent response to a previously unrelated stimulus, either by reward or punishment (as in operant conditioning) or by association of the stimulus with another stimulus that already elicits the response (as in classical conditioning).
a. The process of training that results in physical fitness.
b. The state of physical fitness that results from such training.
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.