A quincunx // is a geometric pattern consisting of five points arranged in a cross, that is five coplanar points, four of them forming a square or rectangle and a fifth at its center. It forms the arrangement of five units in the pattern corresponding to the five-spot on six-sided dice, playing cards, or dominoes. It is represented in Unicode as U+2059 ⁙ five dot punctuation or (for the dice pattern) U+2684 ⚄ die face-5.
Historical origins of the name 
The quincunx was originally a coin issued by the Roman Republic c. 211–200 BC, whose value was five twelfths (quinque + uncia) of an as, the Roman standard bronze coin. On the Roman quincunx coins, the value was sometimes indicated by a pattern of five dots or pellets. However, these dots were not always arranged in a quincunx pattern.
Quincunx patterns occur in many contexts:
- In heraldry, groups of five elements (charges) are often arranged in a quincunx pattern, called in saltire in heraldic terminology. The flag of the Solomon Islands features this pattern, with its five stars representing the five main island groups in the Solomon Islands. Another instance of this pattern occurs in the flag of the Republic of Yucatán, where it symbolized the five departments into which the republic was divided.
- A quincunx is a standard pattern for planting an orchard.
- Quincunxes are used in modern computer graphics as a pattern for multisample anti-aliasing. Quincunx antialiasing samples scenes at the corners and centers of each pixel. These five sample points, in the shape of a quincunx, are combined to produce each displayed pixel. However, samples at the corner points are shared with adjacent pixels, so the number of samples needed is only twice the number of displayed pixels.
- In numerical analysis, the quincunx pattern describes the two-dimensional five-point stencil, a sampling pattern used to derive finite difference approximations to derivatives.
- In architecture, a quincuncial plan, also defined as a "cross-in-square", is the plan of an edifice composed of nine bays. The central and the four angular ones are covered with domes or groin vaults so that the pattern of these domes forms a quincunx; the other four bays are surmounted by barrel vaults.
- A quincunx is one of the quintessential designs of Cosmatesque inlay stonework.
- A quincuncial map is a conformal map projection that maps the poles of the sphere to the centre and four corners of a square, thus forming a quincunx.
- The points on each face of a unit cell of a face-centred cubic lattice form a quincunx.
- The quincunx as a tattoo is known as the five dots tattoo. It has been variously interpreted as a fertility symbol, a reminder of sayings on how to treat women or police, a recognition symbol among the Romani people, a group of close friends, standing alone in the world, or time spent in prison (with the outer four dots representing the prison walls and the inner dot representing the prisoner). Thomas Edison, whose many inventions included a tattooing machine, had this pattern tattooed on his forearm.
- Republican Roman manipular legions adoped a checkered formation called quincunx when deployed for battle.
Literary symbolism 
Various literary works use or refer to the quincunx pattern for its symbolic value:
- The English physician Sir Thomas Browne in his philosophical discourse The Garden of Cyrus (1658) elaborates upon evidence of the quincunx pattern in art, nature and mystically as evidence of "the wisdom of God". Browne possessed several books by the German astronomer Johannes Kepler (1571-1630) including his Ad Vitellionem Paralipomena, (Frankfurt 1604) which is credited as first introducing the pattern to astronomy and astrology in modern times. (OED)
- James Joyce uses the term in Grace, a short story in The Dubliners of 1914, to describe the seating arrangement of five men in a church service. Lobner argues that in this context the pattern serves as a symbol both of the wounds of Christ and of the Greek cross.
- Lawrence Durrell's novel-sequence The Avignon Quintet is arranged in the form of a quincunx, according to the author; the final novel in the sequence is called Quinx, the plot of which includes the discovery of a quincunx of stones.
- The Quincunx (ISBN 0-345-37113-5) is the title of a lengthy and elaborate novel by Charles Palliser set in 19th-century England, published in 1989; the pattern appears in the text as a heraldic device, and is also reflected in the structure of the book.
- In the first chapter of The Rings of Saturn, W.G. Sebald's narrator cites Browne's writing on the quincunx. The quincunx in turn becomes a model for the way in which the rest of the novel unfolds.
- Séamus Heaney describes Ireland's provinces together forming a quincunx, as the Irish word for province cúige (literally: "fifth part") also explicates. The five provinces of Ireland are Ulster (north), Leinster (east), Connacht (west), Munster (south) and Meath (the center). More specifically, in his essay Frontiers of Writing, Heaney creates an image of five towers forming a quincunx pattern within Ireland, one tower for each of the five provinces, each having literary significance.
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- Webster's Collegiate Dictionary, 10th ed., as quoted by Pajares-Ayuela (2001).
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- Lobner, Corinna del Greco (1989), "Equivocation As Stylistic Device: Joyce's "Grace" and Dante", Lectura Dantis 4; for additional work on this instance of the quincunx pattern, see Duffy, Charles F. (1972), "The Seating Arrangement in 'Grace'", James Joyce Quarterly 9: 487–489.
- Gifford, James (1999), "Reading Orientalism and the Crisis of Epistemology in the Novels of Lawrence Durrell", CLCWeb: Comparative Literature and Culture 1 (2), "the most dominant formal element expressing this state of multiplicity in The Avignon Quintet is its quincunx structure".
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