In architecture, a parti is an organizing thought or decision behind an architect's design, presented in the form of a parti diagram, parti sketch, or a simple statement. The term comes from 15th century French, in which "parti pris" meant "decision taken."
The development of the parti frequently precedes the development of plan, section, and elevation diagrams.
Producing a quick sketch (esquisse) of the parti was a critical part of architectural training at the Beaux-Arts de Paris during the 19th and early part of the 20th Century.
In architecture school during the 1900s in the United States, one would have understood the term ‘parti’ as the "main idea" for the planimetric layout of a building. Its roots in the American architectural education system are derived from the Beaux-Arts de Paris. The word "parti" refers to the concept of ‘parti pris’, and refers to the main ‘idea’ of the organizing principle that is embodied in a design and often expressed by a simple geometric diagram. The "parti" often expresses the essence of an architectural design reduced to its essence.
The parti  of the Lonja del Comercio building in Havana (in plan) is a perfect square and based on the classic 9 square problem that was used,  [a] among others, by Peter Eisenman to design some of his houses  and Andrea Palladio in the design of many of his villas.   [b] 
Palladio's plan of the Villa in I quattro libri dell'architettura, 1570
- ^ "A primary protagonist was Rudolf Wittkower, who had published important essays on role of geometry in the works of Alberti and Palladio, essays later collected in Architectural Principles in the Age of Humanism (1949, 1962). The book includes Palladio's Geometry: the Villas, in which Wittkower argues that similar organizational schema underlie all the villas of Palladio. Wittkower's diagrams of the villas are variations of a three-bay by three-bay diagram; a nine-square grid. Wittkower suggests that Palladio's villas can be considered as a single conceptual project based on variations of an ideal plan diagram: “What was in Palladio's mind when he experimented over and over again with the same elements? Once he had found the basic geometric pattern for the problem ‘villa,’ he adapted it as clearly and as simply as possible to the special requirements of each commission. He reconciled the truth at hand with the ‘certain truth’ of mathematics which is final and unchangeable.”
- ^ "The nine-square grid and its progeny can be considered formative in the redirection of pedagogy in American architecture schools, although it was not a pervasive until the late 1970s with the diaspora of the graduates of Cornell, Syracuse, Princeton, and Cooper Union to more and more architecture programs." Ref: Kit-of-Parts Conceptualism: Abstracting Architecture in the American Academy. www
.harvarddesignmagazine .org /issues /19 /kit-of-parts-conceptualism-abstracting-architecture-in-the-american-academy
- ^ Ching, Francis D. K. (1995). A Visual Dictionary of Architecture. Van Nostrand Reinhold Company. p. 53. ISBN 0-442-02462-2.
- ^ James Stevens Curl (2000). "parti.". A Dictionary of Architecture and Landscape Architecture. Oxford University Press. Retrieved May 17, 2009.
- ^ One, Blue (21 November 2012). "An Introduction to Architecture and Visual Communications: parti". Arch100and110.blogspot.com. Retrieved 18 October 2018.
- ^ Mandelbaum, Melissa. "Applying Architecture to Product Design: Parti". Medium.com. Retrieved 18 July 2016.
- ^ Hyungmin Pai, Hyŏng-min Pae, The Portfolio and the Diagram: Architecture, Discourse, and Modernity in America, 2002, ISBN 0262162067, p. 43
- ^ a b "The Parti: A tool for architectural design thinking". Virajita Singh. 22 October 2017. Retrieved 29 April 2021.
- ^ "Harvard Design Magazine: Kit-of-Parts Conceptualism: Abstracting Architecture in the American Academy". www.harvarddesignmagazine.org. Retrieved 29 April 2021.
- ^ "Kit-of-Parts Conceptualism: Abstracting Architecture in the American Academy". Retrieved 2019-12-22.
- ^ https://re.public.polimi.it/retrieve/handle/11311/1039839/247508/FA%2005%20Measures%20and%20Proportions.pdf[bare URL PDF]
- Colin Rowe, “Mathematics of the Ideal Villa,” Mathematics of the Ideal Villa and Other Essays (Cambridge, MA: MIT Press, 1976). First published in Architectural Review, 1947.
- Wittkower, Rudolf, "Architectural principles in the age of humanism," London, Warburg Institute, University of London, 1949.