Difference between Anomaly and Abnormality

Key Difference: Anomaly and Abnormality are in fact synonyms as they both refer to ‘something that is not normal.’

The two words, anomaly and abnormality are often used interchangeably. This is because they both refer to something that is not normal. According to the Oxford Dictionaries, the definition of Anomaly is “Something that deviates from what is standard, normal, or expected.’

On the other hand, Oxford defines Abnormality as “An abnormal feature, characteristic, or occurrence” or “the quality or state of being abnormal.” Abnormal is defined as “Deviating from what is normal or usual, typically in a way that is undesirable or worrying.” Hence, abnormality also refers to something that deviates from what is standard, normal, or expected. Consequently, it can be deduced that Anomaly and Abnormality are in fact synonyms as they both refer to ‘something that is not normal.’

While both can be used interchangeably, their implications are different. The term abnormality is generally used in the context of behavior, whereas anomaly is generally used to refer to data. Anomaly refers to something that is not like the other, a thing, object or data that stands out and is different from the set. For example: Sarah has scored high consistently, except in this test. This is an anomaly, because the focus is on the test scores, rather than on Sarah herself. It focuses on the data, i.e. her test scores: 90, 94, 93, and 57. The 57 in this data is the anomaly.

However, if the example was talking about Sarah and her behavior, rather than her test scores, then this would be abnormal. For example: Sarah always studies for hours before her test, but yesterday instead of studying for today’s test, she went to a party. This is abnormal behavior on Sarah’s part. She usually studies, it is not like her to ignore her responsibility and go party instead. Something must have caused her to deviate from her normal behavior.

Additionally, the term abnormality has more of a negative implication. It is nearly always used to refer to something that is bad. Whereas, anomaly may or may not be bad; it is yet to be decided. Also, anomaly refers to the end result, while abnormality refers to function or process. For example: There is an anomaly in the latest diagnostics. Something in the diagnostics is different from the previous results. Another example: There is an abnormality in the system. This implies there something in the system is not working correctly, irrespective of the result.

In psychology, the term abnormality refers to abnormal behavior. This behavior differs from the generally accepted behavior by society or culture. For example, if a man walks around naked, then that would be considered as abnormal behavior as society generally frowns upon nudity. As this behavior deviates from the norm, it is abnormal behavior. Abnormality may also be used to refer to an imbalanced person, i.e. a person who does not behave as per the norms of society. For example: an abnormal person.

The term anomaly has a different meaning in the field of astronomy. Here, anomaly refers to the angular distance of a planet or satellite from its last perihelion or perigee.

Comparison between Anomaly and Abnormality:




Definition (Oxford Dictionaries)

Something that deviates from what is standard, normal, or expected

An abnormal feature, characteristic, or occurrence

The quality or state of being abnormal

Parts of Speech




Not Normal

Not Normal


May be negative, or maybe neutral

May or may not be cause to worry


Is usually cause to worry


Usually in context of data or object

Usually in context of behavior


All of her test scores are in the 90s, except this one, which is in the 50s.

She usually studies diligently before the test, except before this test she decided to go to a party instead.

Image Courtesy: membean.com, flipped.gardenpsychology.co.uk

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Thank you very much for your excellent explanation :) appreicated!

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