Abstract: Modular furniture elements concave can be assembled to form an article of furniture, such as, armchairs, divans, and beds, consist of elements which, in plan, have two or three different but interrelated shapes. In plan, the different shapes are all based on a circle having a radius R. Each element of a first set of elements has a shape, in plan, defined by a convex semi-circular side of radius R and two converging cooncave sides extending from opposite ends of the convex side and merging together at a blunt edge. Each concave side is equal to one quarter of the circumference of a circle of radius R. Each element of a second set has a shape in plan which is defined by two interconnecting convex sides, each being equal to one quarter of the circumference of a circle of radius R. Each element of a third set has a shape in plan which is defined by a convex side equal to three-quarters the circumference of a circle of radius R and a concave side of one quarter the circumference of such a circle.