deviation

American  

[dee-vee-ey-shuhn] / ˌdi viˈeɪ ʃən /

noun

1. the act of deviating.

2. departure from a standard or norm.

3. Statistics. the difference between one of a set of values and some fixed value, usually the mean of the set.

4. Navigation. the error of a magnetic compass, as that of a ship, on a given heading as a result of local magnetism.

5. Optics.

   1. Also called deflection.  the bending of rays of light away from a straight line.

   2. angle of deviation.

6. departure or divergence from an established dogma or ideology, especially a Communist one.

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deviation British  

/ ˌdiːvɪˈeɪʃən /

noun

1. an act or result of deviating

2. statistics the difference between an observed value in a series of such values and their arithmetic mean

3. the error of a compass due to local magnetic disturbances

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deviation Scientific  

/ dē′vē-ā′shən /

1. The difference between one number in a set and the mean of the set.

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Other Word Forms

• deviative adjective
• deviatory adjective
• nondeviation noun

Etymology

Origin of deviation

First recorded in 1375–1425; late Middle English, from Middle French, from Medieval Latin dēviātiōn-, stem of dēviātiō; equivalent to deviate + -ion

Explanation

Anything that varies from the accepted norm or standard is called a deviation. It is common in math and science, but it can refer to anything that differs from the expected. Deviation in nature is an important part of evolution. When something causes a creature’s DNA to change, it creates a deviation, or a changed characteristic. If the deviation makes the organism better able to survive, it passes the change on to its descendants. People are naturally given to change, so there are deviations in critical thought as well as in math and science. Those deviations often account for the creativity that gives rise to new ideas, or theories, or even musical styles.

Example Sentences

“But when you sum them all up together, it’s actually quite a substantial deviation from that standard.”

From Barron's • Mar. 27, 2026

Just as “The Complex” deviates from his first two novels, “Family Planning” and “The Association of Small Bombs” Mahajan’s career trajectory is also a deviation from that of a traditional novelist.

From Los Angeles Times • Mar. 23, 2026

Last week's opening race in Australia saw a large deviation in start performance across the grid.

From BBC • Mar. 12, 2026

On that day, the S&P 500 was trading in overbought territory, which Bespoke and many others define as one standard deviation above the index’s 50-day moving average.

From MarketWatch • Feb. 10, 2026

Despite generations of effort, this proved illusory, because dip and deviation change unpredictably over time.

From "The Invention of Science" by David Wootton

Related Words

• aberration
• alteration
• anomaly
• breach
• detour
• discrepancy
• disparity
• divergence
• diversion
• fluctuation
• inconsistency
• irregularity
• modification
• variance
• variation