# invariant

/ˌɪnˈvɛɹiənt/ (US) · /ɪnvˈeəɹiənt/ (UK) · CEFR C1 · Noun

Source: https://englishreference.com/word/invariant
Updated: 2026-05-11

## Definition

something that stays the same even when other things around it change. You see this word most often in math or computer science.

For teachers: a value, property, or condition that remains unchanged throughout a specific operation or transformation. Often used in formal logic and programming to ensure system stability.

## Examples

- The speed of light is a physical invariant.
- In this algorithm, the total number of items in the list must remain an invariant during the sorting process.
- The mathematician proved that the topological invariant remained constant regardless of how the shape was stretched or twisted, provided it was not torn.

## Usage notes

- Commonly used in technical contexts like mathematics, physics, and software engineering.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.