Anomaly (noun)

1. Something that deviates from what is standard, normal, or expected.
2. A deviation from the normal or common order, form, or rule.

Origin:

Late middle english: from latin anomalus, from greek anōmalos, from an- "not" + ōmos "level", from ōmai "fit".

Examples:

1. The heat wave was an anomaly in an otherwise mild summer.
2. There are a few anomalies in the data that need to be addressed.
3. The child's ability to read at such a young age was an anomaly.
4. The stock market's sudden drop was an anomaly in an otherwise steady trend.
5. It was an anomaly in the otherwise perfect record of the team.