| reaction (def. 8). |
[ree-ak-shuh
n] 
| 1. | a reverse movement or tendency; an action in a reverse direction or manner. |
| 2. | movement in the direction of political conservatism or extreme rightism. |
| 3. | action in response to some influence, event, etc.: the nation's reaction to the President's speech. |
| 4. | Physiology. action in response to a stimulus, as of the system or of a nerve, muscle, etc. |
| 5. | Medicine/Medical.
|
| 6. | Bacteriology, Immunology. the specific cellular response to foreign matter, as in testing for allergies. |
| 7. | Chemistry. the reciprocal action of chemical agents upon each other; chemical change. |
| 8. | Also called nuclear reaction. Physics. a process in which a nucleus that is bombarded by a photon, particle, or other nucleus, emits a nucleon, alpha particle, or the like, without a significant change in its atomic weight. |
| 9. | Mechanics. the instantaneous response of a system to an applied force, manifested as the exertion of a force equal in magnitude but opposite in direction to the applied force. |
| 10. | Commerce. a decline in the market after an advance in prices. |
A reaction that changes the number of protons or neutrons in the nucleus of an atom. There are several kinds of nuclear reactions, including the fragmentation of large nuclei into smaller ones (nuclear fission), the building up of small nuclei into larger ones (nuclear fusion), and changes begun by collisions with elementary particles or other nuclei (as in particle accelerators).
reaction
reaction re·ac·tion (rē-āk'shən)
n.
A response of an organism or living tissue to a stimulus.
The state resulting from such a response.
A chemical change or transformation in which a substance decomposes, combines with other substances, or interchanges constituents with other substances.
The response of cells or tissues to an antigen, as in a test for immunization.
A pattern of behavior constituting a mental disorder or personality type.
