# deviation

/ˌdiviˈeɪʃən/ (US) · /dˌiːvɪˈeɪʃən/ (UK)

Source: https://englishreference.com/word/deviation
Updated: 2026-08-08

## Senses

### 1. change from the norm

noun · CEFR B2

a difference from what is usual or expected.

For teachers: the act of departing from an established course, principle, or standard.

- Any deviation from the original plan must be approved by the manager.
- The committee noted a significant deviation from the safety protocols during the inspection of the chemical plant.

### 2. statistical difference

noun · CEFR C1 · Technical

the difference between a particular value and the average value of a group.

For teachers: the difference between an observed value and the arithmetic mean of a distribution.

- The standard deviation shows how much the test scores vary from the average.
- A low standard deviation indicates that the data points tend to be very close to the mean of the set.

Usage: Often used in the phrase 'standard deviation' to describe how spread out numbers are.

### 3. change in route

noun · CEFR B2

a move away from a planned path or direction, such as a plane changing course to avoid a storm.

For teachers: a physical departure from a planned or regular course, especially in navigation or transport.

- The pilot requested a deviation to the south to avoid the heavy clouds.
- The ship's deviation from its charted course was necessary to avoid the approaching hurricane, though it delayed the arrival by two days.

## Examples

- His behavior showed a strange deviation from the norm.
- The project timeline suffered a minor deviation due to unexpected weather delays.
- Statistical analysis revealed a significant deviation in the data set, suggesting that the initial hypothesis required revision.

---

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.