a deviation from the common rule, type, arrangement, or form.

someone or something anomalous

With his quiet nature, he was an anomaly in his exuberant family.

an odd, peculiar, or strange condition, situation, quality, etc.

an incongruity or inconsistency.

Astronomy . a quantity measured in degrees, defining the position of an orbiting body with respect to the point at which it is nearest to or farthest from its primary.

Meteorology . the amount of deviation of a meteorological quantity from the accepted normal value of that quantity.

Grammar . irregularity.

noun

conformity , normality , regularity , standard , usual , usualness

noun

aberration , abnormality , departure , deviation , eccentricity , exception , incongruity , inconsistency , irregularity , oddity , peculiarity , rarity , unconformity , unorthodoxy , aberrance , aberrancy , deviance , deviancy , preternaturalness , unnaturalness