Aberration
(1) A deviation or irregularity.
For example, a chromosome aberration is a deviation from the normal chromosome number or the normal chromosome structure.
In this sense, aberration is also synonymous with deflection, departure, divergence, diversion, turning.
(2) A mental aberration is a significant deviation from normal mental activity.
In this sense, aberration is synonymous with mental derangement, mental illness, psychopathy