triangle
A building plan with three dominant straight sides, allowing unequal lengths and slightly rounded or chamfered corners.
A triangular building has a dominant footprint with three straight sides. It can be any kind of a triangle, whether equilateral, isosceles, or scalene. The angles may all be acute, or one may be right or obtuse. The sides may meet at rounded or slightly chamfered angles, as long as the basic shape does not deviate significantly from a triangle.
The principal footprint has three sides, whether their lengths are all equal, two are equal, or all differ. Right-angled and obtuse triangles are included along with acute triangles.
A small corner chamfer can remain a detail of the triangular form without becoming another dominant side. A pentagon or other polygonal plan is identified by its own principal outline rather than by counting every short corner segment.