ANOMALY

[noun] [formal] - a person or thing that is different from what is usual, or not in agreement with something else and therefore not satisfactoryStatistical anomalies can make it difficult to compare economic data from one year to the next. [C]The anomaly of the social security system is that you sometimes have more money without a job. [U]Is it not something of an anomaly to have a president of one political persuasion and a prime minister of another? [C]