Entitled: "Hermaphrodite twins. Woodcut from Pare's works, London 1649." Historically, the term hermaphrodite has also been used to describe ambiguous genitalia and gonadal mosaicism in individuals of gonochoristic species, especially human beings. The word intersex has come into preferred usage for humans, since the word hermaphrodite is considered to be misleading and stigmatizing. Intersex, in humans and other animals, is a variation in sex characteristics including chromosomes, gonads, or genitals that do not allow an individual to be distinctly identified as male or female. Such variation may involve genital ambiguity, and combinations of chromosomal genotype and sexual phenotype other than XY-male and XX-female. Twins are two offspring produced by the same pregnancy. Twins can either be monozygotic (identical), meaning that they can develop from just one zygote that will then split and form two embryos, or dizygotic (fraternal), meaning that they can develop from two different eggs, each are fertilized by separate sperm cells.