- a person or thing occurring singly, especially an individual set apart from others.
- a child or animal that is the only one born at one birth: a research program involving twins and singletons.
- an only child in a family.
- an unmarried person; a single.
- a card that is the only one of a suit in a hand.
- a set consisting of one given element.
- an original holding of one card only in a suit
- a single object, individual, etc, separated or distinguished from a pair or group
- a set containing only one member
- a person who is neither married nor in a relationship
