What does covary mean?
"Covary" is a verb used almost exclusively in scientific and statistical writing to describe the relationship between two or more variables that change together: as one rises or falls, the other tends to rise or fall in a corresponding, measurable way. For example, a researcher might note that hours of exercise covary with self-reported mood scores, meaning shifts in one are systematically linked to shifts in the other. Covariation does not by itself establish that one variable causes the other — it signals only an association — which makes the word especially important in discussions of correlational evidence. Derived forms include "covariance" (the statistical measure of how much two variables change together), "covariation", and "covariate" (a variable included in a model because it may influence the outcome). The term comes from the prefix "co-", meaning "together", combined with "vary", from the Latin "variare", "to change". Though rare in casual speech, "covary" is indispensable vocabulary for anyone reading empirical research.
verb(Of two or more variables) to change together in a way that reflects a statistical relationship; to exhibit variation that is correlated across cases.
- (statistics and science) Of two or more variables or traits, to vary together such that changes in one are systematically associated with changes in the other.
"In the study, income and educational attainment were found to covary across all regions surveyed."
"Height and weight typically covary across a population."
"The researchers observed that anxiety scores covaried with sleep quality in both cohorts."
When scientists say two things 'covary', they mean the variables move in lockstep — and spotting that dance is often the first clue to a hidden cause.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of covary
"Covary" combines the prefix "co-", from the Latin "cum" meaning "with" or "together", with the verb "vary", which derives from the Latin "variare" ("to change") via Old French "varier". The compound emerged in English scientific usage, likely in the nineteenth century as statistics matured into a formal discipline, though the precise date of first attestation is uncertain. It shares its root with words such as "variable", "variance", and "variety".
Related word forms
How covary is actually used
"Covary" is a formal, technical term used chiefly in statistics, psychology, biology, and social sciences. It appears rarely in everyday conversation. It is usually followed by "with" when specifying what it varies alongside.
Easily confused with covary
"Carry" means to transport or support something, while "covary" is a technical term meaning two variables change together in a correlated way.