# Single-Instance Need

> A precondition that exactly one instance of a type must exist across the system.

Record: `lex:single-instance-need`
Kind: constraint
Layer: [Design Patterns Core](https://banes-lab.com/records/layer/design-patterns-core.md)
Canonical: https://banes-lab.com/ontology/lexicon#lex-single-instance-need

## category

- [Creational Patterns](https://banes-lab.com/records/lex-category/creational-patterns.md)

## referenced-by

- [Singleton Pattern](https://banes-lab.com/records/arch/singleton-pattern.md)