lacuna /ləˈkjuːnə 
/ ▸ noun (plural lacunae /ləˈkjuːniː/) (plural or lacunas)
1 an unfilled space; a gap: the journal has filled a lacuna in Middle Eastern studies.
▪ a missing portion in a book or manuscript.
2 Anatomy a cavity or depression, especially in bone. – ORIGIN mid 17th century: from Latin, ‘pool’, from lacus ‘lake’.
EnglishOxford Dictionary of English
