What does outlier mean?
An outlier is a person, object, observation, or group that stands noticeably apart from the others in a larger population. In statistics, the term usually refers to a data value that differs so sharply from the pattern of the rest of the data that it may warrant investigation; it can be a genuinely unusual case, a measurement error, or the result of a different process. In everyday and social contexts, an outlier is someone who does not fit the prevailing group, though the expression often suggests independence, eccentricity, or unconventional thinking rather than a precise statistical category. The word is useful because it names difference in a way that emphasizes relation: an outlier is identified by comparison with a larger group, not by its features alone. It is common in research, business, data analysis, education, and discussions of organizations and creative work.
nounA person, thing, observation, or group that is markedly different from the others in a larger population. In statistics, an outlier is a data value that lies far from the general distribution or pattern.
- A person, object, or group that stands apart from, or differs markedly from, the members of a larger group.
- A data point or observation that lies far from the general distribution or pattern in a set of data.
"The research team identified an outlier in the results and examined it for possible data-entry errors."
"Her unconventional approach made her an outlier in the traditionally conservative department."
"The box plot revealed several outliers, suggesting that the data might contain errors or a separate subgroup."
The regular plural is used when referring to multiple unusual people or things, observations, or values.
"The model flagged several outliers for further review."
The word’s core idea is spatial: an outlier is something lying “out” beyond the group—before statistics gave the term a numerical life.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does outlier come from?
Outlier is an English compound formed from out and lier, an old form based on lie, meaning to be situated apart. The word has been used since the 17th century for something lying outside the main group or area, and its statistical application developed from the same general sense of a value outside the normal range. Its roots are native English rather than a loan from Latin.
Related word forms
How outlier is actually used
Broadly neutral and used in British and American English. In technical writing, especially in statistics and data analysis, it has a more specific meaning; in social contexts, it can imply that someone is independent, eccentric, or resistant to group conformity.
Easily confused with outlier
An outlier is something notably different from a group or pattern, whereas an outlet is an opening, channel, or commercial route through which something is released or sold.