Something that deviates from the norm is anomalous. Something anomalous can be good, such as an exciting new direction in music or art. But that anomalously low score on your math test? Not so good.
To find the origins of the word anomalous we can go back to the Greek anṓmalos, meaning "uneven or irregular." Something that is anomalous is not just different; it is also unexpected, and may even be completely inconsistent with the norm. For example, the recent discovery of ice, and therefore water, on the moon was anomalous to all previous ideas that the moon was lifeless. .