I don't speak Latin and I can't think of a non-dumb way to ask this.

But my understanding is that capita is the plural form of caput.

So I'm wondering how "per capita" makes any sense, then, as it means "per head", not "per heads". Seems like a contradiction in terms to me.

Did Latin itself even have this term at all? Or was this a much later invention by someone who didn't know better and was just trying to be fancy.

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    A very Cerberean question. – Cerberus Sep 6 '19 at 20:11

Apparently an early usage was in inheritance law, in contrast with "per stirpes". Suppose A has children B and C, and B has child D, while C has children E and F. If A outlives his children but not his grandchildren, then with a per capita rule, D, E, and F each get 1/3 of the estate, but under a per stirpes rule, D gets 1/2 and E and F get 1/4 each. In that usage, the plural makes sense--one really does mean something like a division of property "by heads" as opposed to "by lineages". The phrase probably then got pulled into other contexts (like expressing the units of the denominator of a ratio) where the plural is incorrect without people really thinking about it....

I should also add that ancient Roman law on intestate succession used both of these ideas. If direct agnatic descendants survived, the estate was divided per stirpes among all agnatic descendants whose fathers (and paternal grandfathers, etc.) were dead, but if only collateral agnatic relations survived, the estate was divided per capita among the closest class of surviving agnatic relations.

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  • Very interesting. So basically we're looking at two separate meanings of per. The original usage not being "à, for each", but rather "by, in accordance with". And then precisely because it was actually used, it became a fixed phrase of sorts, which resist change even when adopted for new usages. So once people wanted to use the per in it in the other meaning, they just kept the rest of it as is. That makes sense. I'll wait a bit to see if others have something else to chip in, but so far this looks quite convincing. – ЯegDwight Sep 7 '19 at 9:32
  • @ЯegDwight It's worth noting that the Latin per is quite different from the English per, although there's some overlap. Maybe a misanalysis of the preposition has played a role in reanalyzing per capita to work in other contexts. – Joonas Ilmavirta Sep 7 '19 at 11:52
  • @ЯegDwight Just to clarify, prepositions are such versatile little words that enumerating the meanings of a preposition is challenging. People with different linguistic backgrounds will count differently since there will be shades of meaning some of them perceive as being distinct but others do not. So it might be best not to talk about "the other meaning" of per, as if there were only two... – C Monsour Sep 7 '19 at 12:49
  • +1. I find your answer very insightful, yet I resist assuming the grammar is wrongly applied without anyone thinking of it. Could be that the phrase is the short version of some broader expression? I mean, could there be an omitted noun? – Rafael Sep 7 '19 at 13:29
  • @Rafael I can't exclude other possibilities, but incorrect grammar is more common when expressions are adapted by non-native speakers, which is what I suspect happened here. – C Monsour Sep 9 '19 at 9:12

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