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Latin reflexus, past participle of reflectere to reflect


  • 1a archaic : reflected heat, light, or color
b : a mirrored image
c : a copy exact in essential or peculiar features
  • 2a : an automatic and often inborn response to a stimulus that involves a nerve impulse passing inward from a receptor to a nerve center and thence outward to an effector (as a muscle or gland) without reaching the level of consciousness — compare habit
b : the process that culminates in a reflex and comprises reception, transmission, and reaction —called also reflex action
c plural : the power of acting or responding with adequate speed
d : a way of thinking or behaving


A reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. In most contexts, in particular those involving humans, reflex actions are mediated via the reflex arc; this is not always true in other animals, nor does it apply to casual uses of the term 'reflex'.

  • Reaction time

For a reflex, reaction time or latency is the time from the onset of a stimulus until the organism responds. In animals, reaction time to visual stimuli is typically 150 to 300 milliseconds.[1]