Arrhenotoky (from Greek -τόκος -tókos "birth of -" + ἄρρην árrhēn "male person"), also known as arrhenotokous parthenogenesis, is a form of  parthenogenesis in which unfertilized eggs develop into males. The set of processes included under the term arrhenotoky depends on the author. Arrhenotoky may be restricted to the production of males that are haploid, or include diploid males that permanently inactivate one set of chromosomes (parahaploidy) or be used to cover all cases of males being produced by parthenogenesis (e.g. aphids where the males are XO diploids). However, when both males and females develop from unfertilized eggs, the term "deuterotoky" is usually used instead.