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.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.
American Heritage Dictionary Products
The American Heritage Dictionary, 5th Edition
The American Heritage Dictionary of Idioms
The American Heritage Roget's Thesaurus
Curious George's Dictionary
The American Heritage Children's Dictionary
The American Heritage Dictionary of Indo-European Roots
The American Heritage Student Grammar Dictionary
The American Heritage Desk Dictionary + Thesaurus
The American Heritage Science Dictionary
The American Heritage Dictionary of Business Terms
The American Heritage Student Dictionary
The American Heritage Essential Student Thesaurus