Zoophilia, from the Greek ζῶον (zṓon, "animal") and φιλία (philia, "friendship" or "love"), is an affinity or sexual attraction by a human to a non-human animal. Such individuals are called zoophiles. The more recent terms zoosexual and zoosexuality describe the full spectrum of human/animal orientation. A separate term, bestiality (more common in mainstream usage and frequently but incorrectly seen as a synonym; often misspelled as "beastiality"), refers to human/animal sexual activity. To avoid confusion about the meaning of zoophilia — which may refer to the affinity/attraction, paraphilia, or sexual activity — this article uses zoophilia for the former, and zoosexual activity for the sexual act. The two terms are independent: not all sexual acts with animals are performed by zoophiles; and not all zoophiles perform zoosexual acts.
While sexual zoophilia is legal in a few countries (see: legal aspects), it is not explicitly condoned anywhere today, and in most countries sexual acts with animals are illegal under animal abuse laws or, less commonly, laws dealing with crimes against nature. Philosopher and animal liberation author Peter Singer argues that zoophilia is not unethical if there is no harm or cruelty to the animal, but this view is not widely shared, with the majority opinion supporting the view that animals, like children, are not capable of informed consent.
There is currently considerable debate in psychology over whether certain aspects of zoophilia are better understood as an aberration (or paraphilia) or as a sexual orientation. The activity or desire itself is no longer classified as a pathology under DSM-IV (TR) (the Diagnostic and Statistical Manual of the American Psychiatric Association) unless accompanied by distress or interference with normal functioning on the part of the person. Critics point out that that DSM-IV says nothing about acceptability or the well-being of the animal, and many critics outside the field express views that sexual acts with animals are always either abusive or unethical.