Hiatus
An opening, as in the diaphragm.
When there is an unusually wide opening in the diaphragm, there can be a hiatus (or hiatal) hernia.
In Latin an hiatus is 'an opening, gaping mouth, or chasm.' It is derived from the verb 'hiare' meaning 'to gape or yawn.' Therefore, a 'hiatus' is a gaping opening in anything, such as the opening in a cliff leading into a cave or a break in the conversation in which nothing happens or is said.