The term possum covers about 70 species of marsupials native to Australia and surrounding islands. Opossum covers over 100 species of marsupials living in the Western Hemisphere. Opossums are often referred to colloquially as possums (or ‘possums), but in scientific contexts, possum and opossum refer to different groups of animals.
Examples
Opossum only refers to the Western marsupials. So, for example, these writers use the word correctly:
We saw an opossum in our backyard last week. Have they always lived in Michigan? [letter to Detroit Free Press]
In the Appalachian Mountains, prepare to greet Virginia opossum and domestic cats. [Cumberland Times-News]
Opossum is sometimes shortened to possum—for example:
I am thankful the Pilgrims found a turkey before they saw a ‘possum. [Chattanoogan]
First a bear takes off on the red sled and is soon joined by a rabbit, moose, squirrel, possum, and two raccoons, awaken from their winter slumber. [The Missourian]
And the Australian animals are possums—for example:
The brushtail possum, which is native to Australia, was recently spotted by wildlife cameras … [Huffington Post]
Two years after possums were found in medical supplies … plans to redevelop the dilapidated Hornsby Ku-ring-gai Hospital have materialised. [Sydney Morning Herald]
