Merriam-Webster's Word of the Day for March 18, 2023 is: lacuna \luh-KOO-nuh\ noun

Lacuna is a formal word that refers to a gap or blank space in something—in other words, a missing part. When used with respect to biology, lacuna also refers to a small cavity, pit, or discontinuity in an anatomical structure.

// The absence of hemlock pollen from one stretch of the fossil record is a notable lacuna that suggests the tree may have once suffered from some type of blight that nearly wiped out the species.

// An [osteocyte](https://www.merriam-webster.com/dictionary/osteocyte) is a cell that is isolated in a lacuna of bone.

[See the entry >](https://www.merriam-webster.com/dictionary/lacuna)

Examples:

“When civil war broke out in 1642, the ensuing chaos was disastrous. ... In her new novel, ‘The Manningtree Witches,’ A.K. Blakemore explores the consequences of that chaos for a group of village women through the viewpoint of a narrator named Rebecca West. West, a true historical figure, was among those prosecuted in Essex. Blakemore’s novel adheres to these events but fills in the lacunae in the documents.” — Lorraine Berry, The Los Angeles Times, 23 Aug. 2021

Did you know?

If you find yourself drawing a blank when it comes to the definition of lacuna, it might help to imagine drawing water instead, ideally from a lake or lagoon. Lacuna, lake and [lagoon](https://www.merriam-webster.com/dictionary/lagoon) all come ultimately from lacus, the Latin word for “lake.” Latin speakers modified lacus into lacuna to form a word meaning “pit,” “gap,” or “pool.” When English speakers borrowed the term in the 17th century, they used it to refer to a figurative gap in or missing portion of something, such as information or text. (Note that lacuna comes with two plural options: the Latin lacunae \luh-KYOO-nee\ or \luh-KOO-nye\ or the anglicized lacunas \luh-KOO-nuz\\.) Lagoon, meanwhile, hewed closer to the Latin lacuna, referring first to a shallow sound, channel, or pond near or connected to a larger body of water, and later to a shallow artificial pool or pond.