Contravariance

noun

noun ·Rare ·Advanced level

Definitions

Noun
  1. 1
    The reversal of the order of data types acted upon by an operator. countable, uncountable

    "I get why with covariance I can return a Dog (a Dog is a Mammal), but why does contravariance work the other way? Shouldn't it accept a derived type when it expects a base type? Contravariance is consistent with Postel's Law: […]"

  2. 2
    A functor which reverses composition. countable, uncountable
  3. 3
    Of vectors, the property of scaling inversely with a change of basis, as opposed to covariance. countable, uncountable

Synonyms

All synonyms
covariance

Example

More examples

"I get why with covariance I can return a Dog (a Dog is a Mammal), but why does contravariance work the other way? Shouldn't it accept a derived type when it expects a base type? Contravariance is consistent with Postel's Law: […]"

Etymology

From contra- + variance.

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Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.