Part of Speech: Noun
Meaning: An arrangement of five objects so that four form the corners of a square and the fifth marks the center (see the illustration).
Notes: I had to include this bizarre little word in our series as a curiosity—a real word but curiously spelled and pronounced. A quincunx is a quincuncial (the adjective) arrangement of items that are arranged quincuncially (the adverb). A quincuncial arrangement is often repeated, especially in planting trees in an orchard, leaving the impression of diagonal rows, as in the illustration to the left.
In Play: A quincunx may be part of a decorating scheme: "Gay LaVente placed the candles in a perfect quincunx on the table as though they had some sort of secret meaning to her." It is also a farming tool: "Lynn Seed laid out her entire garden in overlapping quincunxes."
Word History: We are obviously dealing with a Latin word copied letter for letter out of that language: quincunx "five-twelfths". This word came from the name of a Roman coin bearing this pattern worth five-twelfths of an as, a standard unit of Roman currency. The word is based on quinque "five" + uncia "twelfth part", oddly derived from unus "one". Whatever its origins, Old English borrowed it as ynce "a twelfth". Over the course of Middle English, this word wandered off in two directions, becoming inch, a twelfth of a foot, and ounce, a twelfth of a pound in Troy weight though 1/16 of a pound Avoirdupois, which we now use. (Many thanks to Lee Blue for suggesting quincunx, a word that defies Dr. Goodword's ability to work Good Words into acknowledgements like this.)