extinction

UK: /ɪkˈstɪŋkʃ^ən/ US: /ɪkˈstɪŋkʃən/ ,(ik stingk′shən)

WordReference Random House Unabridged Dictionary of American English © 2025

ex•tinc•tion  (ik stingk′shən), n. 

1. the act of extinguishing.
2. Biology the fact or condition of being extinguished or extinct.
3. suppression;
   abolition;
   annihilation:
   the extinction of an army.
4. Biology the act or process of becoming extinct;
   a coming to an end or dying out:
   the extinction of a species.
5. Psychology the reduction or loss of a conditioned response as a result of the absence or withdrawal of reinforcement.
6. Astronomy the diminution in the intensity of starlight caused by absorption as it passes through the earth's atmosphere or through interstellar dust.
7. Optics, Crystallography [Crystall., Optics.] the darkness that results from rotation of a thin section to an angle (extinc′tion an′gle)at which plane-polarized light is absorbed by the polarizer.

• Latin ex(s)tinctiōn- (stem of ex(s)tinctiō). See extinct, -ion
• late Middle English extinccio(u)n 1375–1425

Collins Concise English Dictionary © HarperCollins Publishers::

extinction / ɪkˈstɪŋkʃən/, extincture / ɪksˈtɪŋktʃə/ noun

1. the act of making extinct or the state of being extinct
2. the act of extinguishing or the state of being extinguished
3. complete destruction; annihilation
4. reduction of the intensity of radiation as a result of absorption or scattering by matter
5. a process in which the frequency or intensity of a learned response is decreased as a result of reinforcement being withdrawn
   Compare habituation

WordReference Random House Learner's Dictionary of American English © 2025

ex•tinct /ɪkˈstɪŋkt/   adj. 

1. Biology no longer in existence:
   an extinct species.
2. no longer in use; obsolete:
   an extinct custom.
3. no longer active:
   an extinct volcano.

ex•tinc•tion /ɪkˈstɪŋkʃən/  n. [uncountable]

WordReference Random House Unabridged Dictionary of American English © 2025

ex•tinct  (ik stingkt′), adj. 

1. Biology no longer in existence;
   that has ended or died out:
   an extinct species of fish.
2. no longer in use;
   obsolete:
   an extinct custom.
3. extinguished;
   quenched;
   not burning.
4. having ceased eruption;
   no longer active:
   an extinct volcano.

• Latin ex(s)tinctus put out, quenched, past participle of ex(s)tinguere to extinguish
• late Middle English 1400–50

Synonyms

• 1. defunct, gone, vanished. See dead. 
• 2. archaic.
• 3. out.