Abnormality

Definition

A measurable or observable departure from the typical form, structure, function, or behavior expected for a given species, population, or developmental stage; in arthropods, often refers to teratological variants, gynandromorphs, or environmentally induced phenotypic deviations.

Etymology

From Latin abnormis, 'deviating from a rule,' from ab- 'away from' + norma 'rule, pattern.'

Example

A butterfly with bilateral gynandromorphism—male coloration on one side of the body and female on the other—represents a striking morphological abnormality caused by disruption of early embryonic cell division.

Synonyms

• anomaly
• teratism
• deviation
• atypicality

Related Terms

• gynandromorph
• teratology
• phenotypic plasticity
• malformation
• deformity
• ectopic
• asymmetry
• mutation

Usage Notes

In entomological literature, 'abnormality' often carries less causal specificity than 'teratism' (implying developmental defect) or 'mutation' (implying heritable genetic change). The term is frequently used descriptively in collection and survey contexts without implying mechanism—specimens may be labeled simply 'abnormal' when the origin (genetic, environmental, pathogenic) is unknown. Contrast with 'variant,' which typically denotes normal intraspecific variation, and 'aberration,' which in lepidopterology sometimes refers to minor color or pattern deviations rather than structural defects.