a. A machine or mechanical appliance.
b. The arrangement of connected parts in a machine.
2. A system of parts that operate or interact like those of a machine: the mechanism of the solar system.
3. An instrument or a process, physical or mental, by which something is done or comes into being: "The mechanism of oral learning is largely that of continuous repetition" (T.G.E. Powell).
4. A habitual manner of acting to achieve an end.
5. Psychology A usually unconscious mental and emotional pattern that shapes behavior in a given situation or environment: a defense mechanism.
6. The sequence of steps in a chemical reaction.
7. Philosophy The doctrine that all natural phenomena are explicable by material causes and mechanical principles.
[New Latin mēchanismus, from Late Latin mēchanisma, from Greek mēkhanē, machine; see MECHANIC.]
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.