A falx, in the medical sense, means a membrane forming a partition between two entities which is the case in the brain and cerebellum. The falx cerebri is a part of the encephalon and is placed vertically between the two cerebral hemispheres. It has the shape of a sickle, the upper part being fixed to the cranium and the lower part forming a half-circle. This membrane is one of the three partitions of the brain, formed by the dura mater that covers and protects the central nervous system. The dura mater is the outermost layer of the three layers (with the arachnoid and pia mater) forming the brain tissue whose role is to protect the nervous system structures.