anomaly

A deviation from a rule or from what is regarded as normal; an outlier.

This ardent exploration, absorbing all his energy and interest, made him forget for the moment the mystery of his heritage and the anomaly that cut him off from all his fellows.

Something or someone that is strange or unusual.

He is an anomaly among his friends in that he's the only one who's unmarried.

Any event or measurement that is out of the ordinary regardless of whether it is exceptional or not.

She disregarded some of the anomalies in the experiment, putting them down to miscalculation.

Any of various angular distances.

A defect or malformation.