Porist

Porist is a rarely used term that refers to a person who studies porisms, a class of propositions in geometry. The term is not standard in modern textbooks but appears in historical and exploratory discussions of porism theory, particularly in relation to the Poncelet porism.

Porisms are geometric statements that describe a property that holds for an entire family of figures even if it holds for a single instance under certain conditions. A famous example is the Poncelet porism: if there exists a polygon simultaneously inscribed in one conic and circumscribed about another, then there are infinitely many such polygons, for any starting point on the inner conic; in other words, the porism asserts a closure property of the family of polygons.

Historically, porists would study the necessary and sufficient conditions for porisms, explore their projective geometry settings, and may have contributed to early investigations in invariant theory. In contemporary mathematics, the term porist is largely historical or informal, and discussions typically refer to porisms and Poncelet porism rather than to practitioners described as porists.

See also porism, Poncelet porism, and projective geometry.