Definition
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-) the same (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.
Examples
- Astronomers spotted an anomaly in the planet's orbit that hinted at an unseen companion.
- The auditors flagged the transfer as an anomaly because it matched no invoice on file.
- One warm winter is an anomaly; thirty in a row are a trend.
Synonyms
irregularity · aberration · outlier · deviation · exception
In TOEFL & 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.