I have a question related to statistical terminology. More specifically, about the hazard ratio.

When describing the ratio between two hazard rates, we use the term "hazard ratio".

The term "hazards ratio" is also used, however, less frequently. While the latter seems more correct (hazards in the plural, since a ratio is between multiple instances), the former seems to be used more extensively.

Both terms have been used in literature since the 1980s. For example: hazard ratio (Biometrika, 1981; DOI: 10.2307/2335811) and hazards ratio (Biometrics, 1985; DOI: 10.2307/2530659)


What is the correct term: "hazard ratio" or "hazards ratio"?

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    $\begingroup$ "Hazard ratio" is pretty clearly more common, while as far as I can see hazards ratio is quite rare; whether you regard it as correct (I do) or not, hazard is the clear convention. $\endgroup$
    – Glen_b
    Commented Mar 1, 2022 at 23:43

1 Answer 1


If we form a compound noun in English by concatenating two nouns (there are other ways) then the usual practice is for the fist to be a singular noun. The related terms risk ratio, odds ratio are examples (odds is a singular of course). We even have examples where the first noun only seems to occur in the singular in compounds like trouser press.

So, having said that, I would regard hazard ratio as the standard form and would think anyone using hazards ratio was trying to make some specific point by doing so.


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