English Reference

Word

immutable

Phoneticsim·mutable

US/ˌɪmˈjutəbəɫ/

UK/ɪmjˈuːtəbəl/

Definition

adj. describing something that cannot be changed or fixed. In programming, it means a value or object that stays the same once it is created.

adj. incapable of being altered or changed. In a programming context, it describes data structures or values that cannot be modified after their initial creation.

Examples

“The constant value is immutable.”

“Using immutable data structures can help prevent bugs in your code by ensuring that once a value is set, it remains the same.”

“Functional programming languages often rely on immutable variables to ensure that the state of the application remains predictable and consistent across different threads of execution.”

Examples

simple

“The constant value is immutable.”

contextual

“Using immutable data structures can help prevent bugs in your code by ensuring that once a value is set, it remains the same.”

complex

“Functional programming languages often rely on immutable variables to ensure that the state of the application remains predictable and consistent across different threads of execution.”

Real-World Examples

“The author has said she believes biological sex is immutable and has been critical of self-declared gender identity, calling it “quasi-religious” and “anti-science”.”
BreakingNews.ie · 24 Aug 2026
“Here are three immutable facts about Brandon Richard Flowers: he was born just outside Las Vegas, Nevada.”
The Guardian · 17 Aug 2026

Etymology

From Middle English immutable, from Latin immūtābilis (“unchangeable”); im- + mutable.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

Domain

Programming

This entry

Level
C1 · Advanced
Frequency
Occasional
Updated

Scan code

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English Reference