Coincidence

A coincidence (often stated as a mere coincidence) is a collection of two or more events or conditions, closely related by time, space, form, or other associations which appear unlikely to bear a relationship as either cause to effect or effects of a shared cause, within the observer's or observers' understanding of what cause can produce what effects.

The word is derived from the Latin cum- ("with", "together") and incidere (a composed verb from "in" and "cadere": "to fall on", "to happen"). In science, the term is generally used in a more literal translation, e.g., referring to when two rays of light strike a surface at the same point at the same time. In this usage of coincidence, there is no implication that the alignment of events is surprising, noteworthy or non-causal.

From a statistical perspective, coincidences are inevitable and often less remarkable than they may appear intuitively. An example is the birthday problem, where the probability of two individuals sharing a birthday already exceeds 50% with a group of only 23.

A "strange coincidence", to use a phrase
By which such things are settled nowadays.

—Lord Byron. Don Juan. Canto vi. Stanza 78.

Famous quotes containing the word coincidence:

“... there was the first Balkan war and the second Balkan war and then there was the first world war. It is extraordinary how having done a thing once you have to do it again, there is the pleasure of coincidence and there is the pleasure of repetition, and so there is the second world war, and in between there was the Abyssinian war and the Spanish civil war.”
—Gertrude Stein (1874–1946)

“This play holds the season’s record [for early closing], thus far, with a run of four evening performances and one matinee. By an odd coincidence it ran just five performances too many.”
—Dorothy Parker (1893–1967)

“Only what is thought, said, or done at a certain rare coincidence is good.”
—Henry David Thoreau (1817–1862)