parti diagram

A quick concept sketch. A parti diagram is a  rough drawing, doodle, or diagram used early in the schematic design process to  represent a design concept. The classic “napkin sketch”.

​Note that a design parti, is not necessarily a diagram. The word is from the French phrase parti pris, meaning to make a decision.  A Pinterest board use to present design concepts can be a parti.
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​A parti diagram is a loose drawing to represent a concept.