When a narrow gap that does not have the character of a true articu­lar cavity with an articular surface and a capsule forms in the centre of a synchondrosis, the articulation becomes transitional from the contiguous to the interrupted type, to joints. This articulation is called a half-joint (hemiarthrosis), e.g. the joint between the two pubic bones, the pubic symphy­sis (symphysis pubica). A hemiarthrosis may form as the result of reverse transition from interrupted to contiguous articulation due to reduction of joints. For instance, in some vertebrates only a gap remains in the interver­tebral disc in place of the articular cavity between the bodies of some of the vertebrae.