What is the polygonal base of a dome that makes the transition from the round dome to a flat wall?

Question

Quizplus · Accepted Answer

A squinch is the polygonal base of a dome that makes the transition from the round dome to a flat wall.
Key Takeaway: In architecture, a squinch is basically a piece of construction that is used to fill in the upper angles of a square room so that it can be a proper base for a dome, usually spherical or octagonal. The squinch was the primitive version of the pendentive, which was developed and popularized in the Byzantine period.

What Is the Polygonal Base of a Dome That Makes