Today's word of the day is:

 

Lacuna

 

Dictionary.com defines lacuna as:

 

noun

a gap or missing part, as in a manuscript, series, or logical argument; hiatus.
Anatomy . one of the numerous minute cavities in the substance of bone, supposed to contain nucleate cells.
Botany . an air space in the cellular tissue of plants.
As discussed above, note how the lacuna  is subdivided into the hiatus and degradation vacuity.