title: Second-order
text: # Second-order
  
  Second-order may refer to:
  
  ## Mathematics
  
  * Second order approximation, an approximation that includes quadratic terms
  * Second-order arithmetic, an axiomatization allowing quantification of sets of numbers
  * Second-order differential equation, a differential equation in which the highest derivative is the second
  * Second-order logic, an extension of predicate logic
  * Second-order perturbation, in perturbation theory
  
  ## Science and technology
  
  * Second-order cybernetics, the recursive application of cybernetics to itself and the reflexive practice of cybernetics according to this critique.
  * Second-order fluid, an extension of fluid dynamics
  * Second order Fresnel lens, a size of lighthouse lens
  * Second-order reaction, a reaction in which the rate is proportional to the square of a reactant's concentration
  
  ## Psychology and philosophy
  
  * Second-order conditioning, a form of learning from previous learning
  * Second-order desire, the desire to have a desire for something
  * Second-order stimulus, a visual stimulus distinguished by an aspect other than luminance
  
  ## Other uses
  
  * Second Order (religious), the cloistered nuns who are affiliated with mendicant orders of friars
  