Singleton

Generally, a singleton is something which exists alone in some way. The word is used in several different areas:

1. Singleton is used to refer to single babies (as opposed to twin or other multiple births)
2. In set theory a singleton is a set with only one element, for example: { 1 }. Note that a set such as { { 1 , 2, 3 } } is also a singleton: the only element is a set (which itself isn't a singleton).
3. In computer programming, a singleton is a common design pattern. It refers to a class which is meant to be instanced once, and only once. It is much like a global variable in functional programming, but a "global class-instance" instead.
4. In the wake of the popularity of the novel and movie Bridget Jones's Diary, the word has also become popular as a (self)description of individuals without romantic partners, particularly applied to 20/30-something females. There is an undertone to this use of ignoring societal pressures towards partnerships.
5. In the game of contract bridge, a singleton has a specific meaning referring to a hand containing only one card of a particular suit, a singleton. Certain bidding systems (notably Acol) add notional value to the hand for a short suit of this type since it exposes the possibility of trumping.
6. Singleton, Australia, a place in New South Wales