1. Physiology Being an involuntary action or response, such as a sneeze, blink, or hiccup.
2. Produced as an automatic response or reaction: reflex opposition to change.
3. Bent, turned, or thrown back; reflected.
a. Physiology An involuntary response to a stimulus.
b. reflexes A person's ability to respond to new or changing stimuli: His quick reflexes make him a good taxi driver.
2. Psychology An unlearned or instinctive response to a stimulus.
3. Linguistics A form or feature that reflects or represents an earlier, often reconstructed, form or feature having undergone phonetic or other change.
a. Something, such as light or heat, that is reflected.
b. An image produced by reflection.
c. A copy or reproduction.
[From Middle English reflexen, to refract light, bend back, from Latin reflexus, past participle of reflectere, to bend back; see REFLECT.]
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.