Sui generis
In local government, a "sui generis" entity is one that does not fit with the general scheme of local governance of a country. For example in England, the City of London and the Isles of Scilly are the two "sui generis" localities, as their forms of local government are both (for historical or geographical reasons) very different from those of elsewhere in the country. 
In a press conference during which reporters were trying to analyse his political personality, Huey Long said, "...say that I am "sui generus", and let it go at that."
South African family law
An engagement, which is an agreement "sui generis", is generally defined in the common law as "a legal agreement between a man and a woman to marry each other on a specific or determinable date." Despite the constitutional developments discussed previously, this definition remains in place today.Consensus is prevented, "inter alia", by mistake, misrepresentation, "metus" and undue influence.