Sui generis
A similar case that led to the use of the label "sui generis" is the relationship of New Caledonia relative to France, because the legal status of New Caledonia can aptly be said to lie somewhere between a French overseas collectivity and a sovereign nation. Although other examples of such status for other dependent or disputed territories may exist, this arrangement is unique within the French realm.
Miss Peregrine's Home for Peculiar Children
Otherwise known as "syndrigast" (a word meaning "peculiar spirit" in the Old Peculiar language, which is in turn the author's adaptation of Old English, or Anglo-Saxon language), peculiar folk are a branch of humanity possessing a second soul which manifests itself in strange ways such as abnormal characteristics and abilities commonly referred to as "peculiarities". Very rarely are peculiar children born to peculiar parents as the essence or gene of peculiarity often skips entire generations, making peculiar population vastly less than that of normal people.