aberration /ab′ərā″shən/ [L, aberrare, to wander] , 1. any departure from the usual course or normal condition. 2. abnormal growth or development. 3. (in psychology) an illogical and unreasonable thought or belief, often leading to an unsound mental state. 4. (in genetics) any change in the number or structure of the chromosomes. See also chromosomal aberration. 5. (in optics) any imperfect image formation or blurring caused by unequal refraction or focalization of light rays through a lens. 6. (in botany and zoology) pertaining to an abnormal individual, such as certain atypical members of a species. −aberrant, adj.
