In real property law, the four characteristics that are peculiar to property owned by several individuals as joint tenants.
The four unities are unity of time, unity of title, unity of interest, and unity of possession.
Unity of time is a characteristic because each joint tenant receives his or her interest at the same time—that is, upon delivery of the deed to the property. Unity of title exists because each tenant receives his or her title from the same grantor, and unity of interest because each tenant owns an undivided interest in the property. Unity of possession exists because each tenant has the right of possession of every part of the whole property.
"Unities." West's Encyclopedia of American Law. . Encyclopedia.com. (September 22, 2018). http://www.encyclopedia.com/law/encyclopedias-almanacs-transcripts-and-maps/unities
"Unities." West's Encyclopedia of American Law. . Retrieved September 22, 2018 from Encyclopedia.com: http://www.encyclopedia.com/law/encyclopedias-almanacs-transcripts-and-maps/unities