deviation

American  

[dee-vee-ey-shuhn] / ˌdi viˈeɪ ʃən /

noun

deviations plural

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.

---

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

---

deviation Scientific  

/ dē′vē-ā′shən /

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

---

Other Word Forms

Derived Forms

• nondeviation
  noun
• deviative
  adjective
• deviatory
  adjective

Inflected Forms

Nouns

• deviations
  plural

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

See Examples For:

deviation deviations

The intervention raised math achievement by 0.184 standard deviation a year in elementary school and 0.146 in secondary school.

From The Wall Street Journal ● Jul. 24, 2026

For purposes of calculating this strategy’s track record, a dip was defined as a drop of at least one standard deviation below the stock market’s trailing 12-month mean.

From MarketWatch ● Jun. 24, 2026

The country’s central bank, Bank Indonesia, has set an inflation target of 2.5 percent for this year and next, with a deviation of one percentage point either way.

From Barron's ● Jun. 2, 2026

It’s the first real deviation from the dead-eyed cycle of his daily life since his wife grabbed her car keys and never looked back.

From Salon ● May 30, 2026

That is just ordinary deviation from external reality.

From "East of Eden" by John Steinbeck

Frequent deviations from intrinsic value represent an opportunity for investors who can recognize patterns and capitalize, Ali said.

From MarketWatch ● Jun. 25, 2026

Our measurement, accepted for publication in Physical Review Letters, shows a tension of four standard deviations from the expectations of the Standard Model.

From Science Daily ● May 26, 2026

The scientists suggested several theories for why these two humpbacks embarked on such "exceptional" deviations from the normal routes.

From Barron's ● May 20, 2026

It also analyzes deviations from a subject’s routine.

From Los Angeles Times ● May 4, 2026

The conversation that follows involves more creative coercion than outright job offer, and there are several deviations into the subjects of the ballet, modern fashion, and Japanese mythology.

From "The Night Circus" by Erin Morgenstern

Related Words

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