Medical Dictionary

reaction re·ac·tion (rē-āk'shən)

  1. A response of an organism or living tissue to a stimulus.

  2. The state resulting from such a response.

  3. A chemical change or transformation in which a substance decomposes, combines with other substances, or interchanges constituents with other substances.

  4. The response of cells or tissues to an antigen, as in a test for immunization.

  5. A pattern of behavior constituting a mental disorder or personality type.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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