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 mathematics, a singleton is a set with exactly 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 is not a singleton). In axiomatic set theory, the existence of singletons is a consequence of the axiom of pairing.
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