noun
singleton
SING-gul-tun/ˈsɪŋɡltən/
A sole member rather than part of a multiple set.
The red sock is a singleton beside three matching pairs.

Etymology
The idea of 'one, separate' first named a lone card of its suit in a hand. Singleton later broadened to other instances of singularity, including a person or thing considered apart from others.
In context
a certain type of twin pregnancies require to definitely a lot more frequent number of ultrasounds in pregnancy just because you have twins compared to a singleton
More examples
- With no other hearts in my hand, the ace is a singleton.
- Unlike her twin brothers, Maya was born a singleton.
- The application uses a singleton to manage its settings.
Forms
singleton · singletons
single adjective — Existing alone rather than with others.
Similar words
- individual
- Emphasizes a separate person or thing, even within a group.
- single
- Often refers to an unmarried person or an individual item.