Definition of "fornix"

(anatomy) An archlike or vaulted structure or fold:

1. The junction where the conjunctiva lining the eyelid meets the conjunctiva overlying the sclera.  examples

2. (neuroanatomy) A triangular area of white matter in the mammalian brain beneath the corpus callosum and between the hippocampus and the hypothalamus.  examples

3. The vaulted upper part of the vagina surrounding the uterine cervix.  examples