Singleton (noun)

1. A person who is single or not married.
2. A playing card with a unique rank and suit in a deck of cards.
3. A mathematical object that has only one element or member.
4. A software design pattern where only one instance of a class is allowed to exist at a time.

Origin:

The word 'singleton' comes from the word 'single' and refers to a person or thing that is singular or unique.

Examples:

1. Jane was a singleton, and she enjoyed her independence and freedom.
2. The singleton was the only card in the deck that could be played in a specific situation.
3. The set of prime numbers was a singleton, with only one member, the number 2.
4. The singleton pattern was used to enforce consistency and prevent conflicts in the software system.
5. As a singleton, John lived a solitary life, but he was content with his simple and quiet existence.