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anomaly

/əˈnɑːməli//əˈnɒməli/·noun
something that deviates from what is normal, standard, or expected
Fig. 1 — Thirty-five lights are pulsing as one, a clean wave going out and coming back, and something in the rhythm is wrong before I can say what.
01Definition

An anomaly is the data point that refuses to behave: the warm winter in a cooling century, the orbit that drifts off its predicted path, the payment that matches no invoice. From the Greek anōmalos, 'uneven' — not (an-) even (homalos). What matters is the background: an anomaly exists only against a field of agreement, and science watches that spot closely, because anomalies are where current theories quietly begin to fail.

02In use
  • iAstronomers spotted a subtle anomaly in the planet's orbit that hinted at an unseen companion.
  • iiThe auditors flagged the transfer as an anomaly because it matched no invoice on file.
  • iiiOne warm winter is an anomaly; thirty in a row are a trend.
03Collocations
  • a statistical anomaly
  • detect an anomaly
  • explain an anomaly
  • an anomaly in the data
  • remain an anomaly

Family anomalous (adjective) · anomalously (adverb)

04Relations

=irregularity, aberration, outlier, deviation, exception

≠the norm, regularity, paradigm

05Compared
PairThe difference
anomaly vs discrepancybreaks the expected pattern, cause unknown → anomaly; two things that should match but don't → discrepancy.
06TOEFL & IELTS

A TOEFL science-passage workhorse: texts introduce an anomaly — a finding the old model cannot explain — and spend the rest of the passage resolving it, so the word often marks the main idea's turning point. Learn the adjective 'anomalous' and the collocations 'detect/explain an anomaly'. It also pairs naturally with 'paradigm': in Kuhn's account, accumulating anomalies are what force a paradigm shift.

07Asked
What is the difference between an anomaly and an outlier?
An outlier is a statistical fact: a point far from the rest, possibly harmless, possibly a typo. An anomaly is a judgment: something that breaks the expected pattern and therefore probably means something — fraud, a fault, a failing theory. Data scientists keep the words apart because outliers get trimmed; anomalies get investigated.
What is anomaly detection?
The field of automatically flagging what doesn't fit: the card transaction unlike your history, the server metric drifting off its rhythm, the scan pixel that breaks the texture. Systems learn 'normal' from mountains of past data, then score each new event by its distance from that pattern — fraud, intrusion and fault detection all run on it.
What does anomaly mean in simple terms?
Something that refuses to match the pattern around it — one warm winter in a cooling century, one payment matching no invoice. The scene above stages the definition: a field of lights pulses as one, drops to black — and a single light is still lit, half a beat behind, caught alone in the open.
What is the plural of anomaly?
Anomalies — the regular -y to -ies change, nothing Greek about the plural despite the word's origin. The adjective is anomalous ('an anomalous result') with its adverb anomalously; there is no verb. 'Detect', 'explain' and 'resolve' are the verbs anomalies actually take.
What is an anomaly scan?
The routine ultrasound offered around 18–21 weeks of pregnancy, which checks the baby's physical development in detail. The name uses the word's neutral clinical sense: an anomaly here is any structural difference from typical development, most of which are minor or need only follow-up. Medical bodies increasingly say 'mid-pregnancy scan' for exactly that reason.
Where does anomaly come from?
From Greek anōmalos: an-, 'not', plus homalos, 'even' — literally unevenness in a smooth surface. It is unrelated to 'anonymous' (no name) and to sociology's 'anomie' (normlessness), two lookalikes it gets tangled with. The root explains the usage: an anomaly needs a smooth background to stand out against.
How are anomalies connected to paradigm shifts?
In Thomas Kuhn's account of science, anomalies are the engine: results the reigning paradigm cannot explain pile up quietly at the edges until the framework itself gives way — Mercury's misbehaving orbit helped retire Newton for Einstein. One anomaly is a puzzle; accumulating anomalies are a revolution on schedule.