COMMISSURE, noun

1. A joint, seam or closure; the place where two bodies or parts of a body meet and unite; an interstice or cleft between particles or parts, as between plates or lamellae.

2. In architecture, the joint of two stones, or application of the surface of one to that of another.

3. In anatomy, a suture of the cranium or skull; articulation; the corners of the lips. Also, certain parts in the ventricles of the brain, uniting the two hemispheres.