Lacuna / luh-KYOO-nuh / noun
plural lacunae / luh-KYOO-nee / or lacunas / Lacuna is from the Latin lacuna, "a cavity, a hollow," from lacus, "a hollow.":
1. A blank space; a missing part; a gap.
2. (Biology) A small opening, depression, or cavity in an anatomical structure.
Like most other writers of his generation, he was a profoundly apolitical being, not from any lacuna in his education but as a matter or principle.
-- Walter Laqueur, "The Artist in Politics", New York Times, May 15, 1983
Between the time of my first memory . . . and my second and third memories, I remember nothing. The lacunae of these years I've been able to fill sketchily from the entries in my baby book, which notes such incidents as my first smile.
-- Jaime Manrique, Eminent Maricones
The exodus of wives, relatives, friends and hangers-on had left a big howling lacuna which wrapped the homestead in webs of glorious nostalgia.
-- Moses Isegawa, Abyssinian Chronicles