Crescent

A crescent is a shape made by taking a circle and removing a slightly smaller circle from one side. What remains is curved on both edges and pointed at both ends, and is widely considered the most elegant way to have a piece missing.^[1]

The best-known crescent is the Moon, which becomes one for a few days each month. The Moon does not actually change shape during this time; it is merely lit from the side, a detail the crescent community regards as a technicality.

Geometry

A crescent has two horns, an inside edge and an outside edge. Mathematicians define the inside edge as the one facing the missing circle, and the outside edge as the one facing everything else, which is most of the universe.^[2]

The Subtractivist controversy

Whether a crescent is a shape in its own right or simply a circle with something missing has divided geometers since 1823. The Subtractivists hold that a crescent is a circle minus a circle. The Additivists hold that a circle is a crescent plus the missing bit, and always has been. Both sides agree that the croissant, whose name is French for “crescent”, should be kept out of it, as it always turns up with crumbs.^[3]

Crescents in daily life

• Croissants: crescents in French, and also in pastry.
• Bananas: crescents that have committed to being fruit.
• Streets called The Crescent, which curve so that every house can see slightly more of the house next door.
• The pale part at the base of a fingernail, a crescent that comes free with every hand.

See also

• Circle – a crescent with nothing missing
• Sun – lights the Moon from the side, on purpose

References

1. Arc, A. (1997). Something Missing. Curve Press.
2. Lune, L. (2008). “On the Outside Edge”. Journal of Most of the Universe, 1: 1.
3. Society of Subtractivists (1823). “A Circle, Minus”. Pamphlet, crescent-shaped.