atypical

Atypical is an adjective that describes something not representative of a group, not typical, or unusual. The word comes from the prefix a- meaning not, combined with typikos, meaning of a type or typical.

In general usage, atypical describes items, events, or behaviors that do not fit standard categories or expectations. It often signals rarity or deviation from what is considered normal within a given context.

In medicine and psychology, atypical denotes presentations that do not follow the common pattern. Examples include atypical pneumonia, which is caused by organisms such as Mycoplasma or Chlamydophila and often shows patchy infiltrates rather than lobar consolidation; and atypical depression, a major depressive disorder subtype characterized by features such as mood reactivity and other distinctive symptoms.

In statistics and data analysis, an atypical data point is an observation that diverges from the overall distribution, sometimes referred to as an outlier or anomaly. Such data points can warrant special consideration in interpretation and modeling.

Atypical also appears in culture and media as a title. The Netflix series Atypical (2017–2021) follows a young man on the autism spectrum and uses the term to signal nonconformity and the complexities of individual experience.

Overall, atypical functions as a broad, neutral descriptor across disciplines, signaling departure from the standard or expected rather than a value judgment about quality.