a parti diagram is an idea sketch, an initial response to a site, a client's program or some other conditions that begin to determine the order for designing a project. They don't really represent what the project will look like in plan or elevation, but are a road map of the ideas of the project. Ideas of 'threshold', 'tension v. repose', 'horizon and center', or 'territory and enclosure' all can be simply diagrammed in the parti as an initial response to the problem posed by a new project.
"... a freehand sketch diagram that was at the tangent between idea and imagination...if the parti - the first critical diagram - is not made well, it will be difficult for architecture to follow. If there is no parti, there will be no architecture, only (at best) little more than the utility of construction. Buried within their early sketches is the germ of a narrative or language. The early diagrams are reflective conversations with the language of architecture."
- Alan Phillips, Brighton, UK
the diagrams above are some of the parti sketches from some recent projects of mine