title: Invariant
text: # Invariant
  
  Invariant and invariance may refer to:
  
  ## Computer science
  
  * Invariant (computer science), an expression whose value doesn't change during program execution
     * Loop invariant, a property of a program loop that is true before (and after) each iteration
  * A data type in method overriding that is neither covariant nor contravariant
  * Class invariant, an invariant used to constrain objects of a class
  
  ## Physics, mathematics, and statistics
  
  * Invariant (mathematics), a property of a mathematical object that is not changed by a specific operation or transformation
     * Rotational invariance, the property of function whose value does not change when arbitrary rotations are applied to its argument
     * Scale invariance, a property of objects or laws that do not change if scales of length, energy, or other variables, are multiplied by a common factor
     * Topological invariant
  * Invariant (physics), something does not change under a transformation, such as from one reference frame to another
  * Invariant estimator in statistics
  * Measurement invariance, a statistical property of measurement
  * Oxford University Invariant Society, an Oxford student mathematics club
  
  ## Other uses
  
  * Invariant (linguistics), a word that does not undergo inflection
  * Invariant (music)
  * Writer invariant, property of a text which is similar in all texts of a given author, and different in texts of different authors
  * Invariance (magazine), a French Communist journal
  * Invariances, a 2001 book by philosopher Robert Nozick
  