Opossums (/əˈpɒsəmz/) are members of the marsupial order Didelphimorphia (/daɪˌdɛlfɪˈmɔːrfiə/) endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 126 species in 18 genera. Opossums originated in South America and entered North America in the Great American Interchange following the connection of North and South America in the late Cenozoic.
The Virginia opossum is the only species found in the United States and Canada. It is often simply referred to as an opossum, and in North America it is commonly referred to as a possum (/ˈpɒsəm/; sometimes rendered as 'possum in written form to indicate the dropped "o"). The Australasian arboreal marsupials of suborder Phalangeriformes are also called possums because of their resemblance to opossums, but they belong to a different order. The opossum is typically a nonaggressive animal and almost never carries the virus that causes rabies.
The word opossum is derived from the Powhatan language and was first recorded between 1607 and 1611 by John Smith (as opassom) and William Strachey (as aposoum). Possum was first recorded in 1613. Both men encountered the language at the English settlement of Jamestown, Virginia, which Smith helped to found and where Strachey later served as its first secretary. Strachey's notes describe the opossum as a "beast in bigness of a pig and in taste alike," while Smith recorded it "hath an head like a swine ... tail like a rat ... of the bigness of a cat." The Powhatan word ultimately derives from a Proto-Algonquian word (*wa·p-aʔθemwa) meaning "white dog or dog-like beast."
Following the arrival of Europeans in Australia, the term possum was borrowed to describe distantly related Australian marsupials of the suborder Phalangeriformes,which are more closely related to other Australian marsupials such as kangaroos.
They similarly have didelphimorphia, two (di) wombs (delphus)