Pronunciation: /ˌæbnɔːˈmælɪti/ · Part of speech: noun · Adjective form: abnormal · Plural: abnormalities

Definition. An abnormality is a form, structure, or condition that is not usual — a feature that deviates from what is considered normal in anatomy, physiology, development, or function. Where the adjective abnormal describes something as unusual, the noun abnormality names the unusual feature or state itself.

General use. The word can refer to a wide range of deviations: a structural defect, an unusual growth, a functional disturbance, or a departure from normal values. Examples include a congenital abnormality (one present at birth), a chromosomal abnormality, a structural abnormality seen on imaging, or a functional abnormality of an organ system.

Use in clinical findings. Abnormalities are central to diagnosis. A clinician may detect an abnormality on examination, in a laboratory result, or on a scan, and then work to determine its cause and significance. As in the quoted example, an abnormality may also be functional and systemic: children with sickle-cell disease have a profound abnormality of the immune system, which makes them more susceptible to infections such as pneumococcal disease. Here the abnormality is not a single visible defect but a disturbance in how a body system works.

Degrees and significance. Like the adjective abnormal, an abnormality is not automatically harmful. Some abnormalities are minor anatomical variants with no consequence; others are clinically important and require treatment. The term simply identifies that something differs from the expected; its impact depends on what it is, how severe it is, and the overall clinical context.

Related terminology (terat- / terato-). As the dictionary note indicates, many specific terms for abnormalities — particularly developmental ones — use the prefixes terat- or terato-, from the Greek teras, meaning “monster” or “marvel.” For example, teratogenic describes an agent that causes developmental abnormalities in an embryo or fetus, teratogenesis is the process by which such abnormalities arise, and teratology is the study of developmental abnormalities. These terms are encountered especially in embryology and in discussions of birth defects.

Distinction from related terms. Anomaly is a close synonym, often used for a structural irregularity. Malformation specifically means a structural defect of development. Deformity implies a distortion of normal shape. Defect stresses something missing or faulty. Abnormality is the broadest of these, covering structural, functional, and developmental deviations alike.

Clinical relevance. Recognising and characterising an abnormality guides further investigation, monitoring, and management. Describing whether an abnormality is congenital or acquired, structural or functional, and significant or incidental helps determine the appropriate clinical response.

Etymology. From Latin abnormis, “deviating from a rule” (ab- = away from + norma = rule, standard), with the noun suffix -ity denoting a state or quality — literally, the state of being away from the standard.

⚠️ Disclaimer: This explanation is provided for general educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional regarding any clinical questions or patient care decisions.