What does incommensurate mean?
Incommensurate means so different from something else that a normal comparison or shared measure does not work. The word is especially useful when describing a severe disproportion: a disaster may be incommensurate with the resources available to respond, or an achievement may be incommensurate with anything that preceded it. Its connotation is generally serious, suggesting that the mismatch is extreme rather than merely imperfect. In mathematics, the term has a more precise meaning. Two quantities are incommensurable when they have no common measure, often because the ratio between them is irrational. The word can therefore connect an ordinary discussion of scale with the technical concept of measurement. Because it is formal and somewhat literary, it is most effective in careful prose rather than casual conversation.
adjectiveNot commensurate: unable to be measured against, compared with, or properly matched to something else. In mathematics, it describes quantities that have no common measure or whose ratio is not rational.
- Not properly matched or proportioned to something else; disproportionately large, small, or serious.
- Unable to be measured against or compared with something else using a common standard.
- Mathematically, describing quantities that have no common measure or whose ratio is not rational.
"The scale of the crisis is incommensurate with the resources currently available to address it."
"The damage was incommensurate with the expectations of the entire project."
"The side lengths of a triangle with irrational ratios are incommensurable, so no single unit measures both exactly."
In mathematics, incommensurate quantities have no common unit; in ordinary speech, the word signals a mismatch so profound that ordinary scales of comparison fall short.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does incommensurate come from?
The word was formed in English from the Latin prefix in-, meaning “not,” and a form related to commensuratus, meaning “measured” or “proportioned.” Its development follows the history of commensurate, which refers to quantities that can be measured by a common standard or compared by a known ratio. The shared Latin root is also reflected in commensurable and commensurability.
Related word forms
How incommensurate is actually used
The adjective is formal and relatively uncommon. It is often used figuratively for a severe mismatch, especially between a problem's scale and the resources, response, or significance available to deal with it. In technical mathematical writing, it specifically indicates that two quantities cannot be related by a rational ratio or common measure.
Easily confused with incommensurate
Both words describe a lack of a measurable or meaningful correspondence, but incommensurable is especially common in mathematical contexts, while incommensurate is more widely used for severe mismatch or disproportion.
Commensurate means appropriately matched or able to be compared by a common measure; incommensurate means the opposite.