What does deviation mean?
"Deviation" is a noun describing the act of turning aside or departing from an established course, standard, rule, or expectation. It can refer to concrete departures — a ship deviating from its plotted route — or abstract ones, such as a deviation from company policy or from social norms. The word is especially prominent in statistics and science, where "standard deviation" measures how widely values in a data set spread around their average; here the term is entirely neutral and technical. In ordinary usage, however, deviation often carries a slightly critical tone, suggesting nonconformity or improper behaviour, particularly in older clinical phrases like "sexual deviation." Derived from the Latin "deviare," meaning "to turn out of the way," it entered English in the early modern period and remains a precise, useful term whenever one wants to emphasise that something has strayed from where it was supposed to be.
nounThe action of departing from an established course, accepted standard, or original state; also, a measurable difference or divergence, especially in statistics.
- The act or instance of departing from an established course, rule, standard, or expected behaviour.
- A noticeable difference or amount of difference between an observed value and a reference value, as in statistics or measurement (e.g., standard deviation).
- (Historical/technical) The deflection of a compass needle caused by local magnetic influences aboard a ship or aircraft.
"The pilot's slight deviation from the flight path was corrected within seconds by the autopilot."
"Any deviation from the agreed contract terms must be approved in writing by both parties."
"The engineer calculated the standard deviation of the sample to assess how tightly clustered the measurements were."
Used when referring to multiple distinct instances of departing from a standard, or to multiple measured divergences in a data set.
"The quality-control report listed several deviations from the manufacturing specification."
In statistics, the 'standard deviation' is so fundamental that it appears in everything from IQ scores to weather forecasts — yet the word itself comes from a Latin verb meaning simply 'to turn off the road.'
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of deviation
"Deviation" derives from the Latin verb "deviare," formed from "de-" (away from) and "via" (road or way), literally meaning "to turn out of the road." English adopted it in the early 17th century via the Late Latin noun form. It shares this root with "devious" and "deviant," all preserving the core image of leaving the proper path.
Related word forms
How deviation is actually used
"Deviation" is largely formal or technical in register; in everyday speech, words like "difference" or "change" are more common. It carries a mildly negative connotation when applied to human behaviour, implying departure from what is considered acceptable — a sense now somewhat dated outside clinical contexts. In statistics and science it is entirely neutral.
Easily confused with deviation
"Diviation" is not a standard English word; the correct spelling is "deviation," which refers to a departure from a standard or norm.