Sui generis

Sui generis (/ˌsuːaɪ ˈdʒɛnərɪs/;Latin: [ˈsʊ.iː ˈɡɛnɛrɪs]) is a Latin phrase, meaning "of its (his, her, or their) own kind; in a class by itself; unique".

The term is widely used to refer to more esoteric entities in a number of disciplines, including

The expression is often used in analytic philosophy to indicate an idea, an entity, or a reality which cannot be reduced to a lower concept or included in a higher concept.

In the taxonomical structure "genus → species", a species is described as sui generis if its genus was created to classify it (i.e., its uniqueness at the time of classification merited the creation of a new genus, the sole member of which was initially the sui generis species). A species that is the sole extant member of its genus (e.g. the Homo genus) is not necessarily sui generis: extinctions have eliminated other species of that genus.

In law, it is a term of art used to identify a legal classification that exists independently of other categorizations because of its singularity or due to the specific creation of an entitlement or obligation. For example, a court's contempt powers arise sui generis and not from statute or rule. The New York Court of Appeals has used the term in describing cooperative apartment corporations, mostly because this form of housing is considered real property for some purposes and personal property for other purposes.

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