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Code & Deliverynoun · /ˈsɪŋɡəltən/

singleton

In simple English

In software engineering, a singleton is a creational design pattern that ensures a class has exactly one instance throughout the application lifecycle. This is useful for managing shared resources like database connections, logging systems, configuration managers, or thread pools. When you implement the singleton pattern, you control how the single instance is created and accessed, typically through a static method like getInstance(). In real tech workplaces, developers discuss singletons when designing systems that need centralized control or when reviewing code to ensure proper resource management. Teams debate whether to use singletons or dependency injection, as singletons can sometimes make testing harder or create hidden dependencies.

Understanding what the singleton design pattern is and when to use it in software architecture.

At a glanceCEFR C1
Commonness4/5
Versatility4/5
FormalityCasualFormalFormal
Spoken ↔ WrittenSpokenWrittenBoth
Directness ↔ DiplomaticDirectDiplomaticDirect
RegionUS and UK
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Say it like this

✓We implemented it as a singleton pattern
✓Make sure the logger is a singleton
✓Avoid singletons when possible; use dependency injection instead

Real examples

in a code review

"This class should be a singleton since we only need one instance managing all user sessions."

in a standup

"I refactored the configuration manager into a singleton so all modules access the same config data."

in a team meeting

"We are debating whether to keep our database connection as a singleton or switch to a connection pool."

Don't say this

Handle with care. Often confused with just having one instance of something; singleton is a specific design pattern with controlled instantiation, not merely having a single object.

✕The singleton ensures we have multiple instances of the class.
✓The singleton ensures we have only one instance of the class.— Singleton by definition restricts the class to a single instance, not multiple instances.
✕We will singleton the database connection.
✓We will implement the singleton pattern for the database connection.— Singleton is typically a noun in this context. You do not use it as a verb directly; you implement the pattern or make something a singleton.
✕This is just a singleton object.
✓This is a singleton instance managed by the singleton pattern.— Any object can exist alone; a singleton is specifically about the design pattern that enforces and controls single instantiation.

Other forms

noun

singleton

"The cache manager is implemented as a singleton."

noun

singletons

"We are reviewing all the singletons in our codebase to reduce coupling."

adjective

singleton

"We used a singleton pattern for the logging service."

Often used with

singleton patternThe design pattern itself; most common phrasing when discussing the architectural approach.
implement a singletonTo code or apply the singleton pattern to a class or resource.
singleton instanceRefers to the actual single object created by the singleton pattern.
make something a singletonTo apply the singleton pattern to a previously non-singleton class.
singleton classA class designed and implemented with the singleton pattern.

Similar words

single instanceMore general; describes having one instance but does not specify the design pattern mechanism.
global instanceEmphasizes the global accessibility aspect but lacks the control and restriction implied by singleton.
static instanceRelates to how singletons are often implemented but is not a full synonym for the pattern itself.

Opposites

multitonfactory patternprototype pattern

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Practice

Try it

4 quick exercises

Pick the most natural phrasing

1. Your team is discussing how to manage the application's configuration file. What would you say?

Complete the sentence

2. The logging service is implemented as a _______ to ensure all modules write to the same log file.

Spot the mistake

3. Which sentence uses 'singleton' incorrectly?

Rewrite naturally

4. Rewrite this in natural tech English using 'singleton': 'We need a design where there is only one object that manages all the caching for the whole application.'

Questions

Quick poll

Have you said "singleton" in a standup this week?

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