As any pedant will tell you, decimate means “to destroy a tenth of something.” Of course, its modern usage has been expanded to this:

  1. to destroy a large number of (plants, animals, people, etc.)

  2. to damage or destroy a large part of (something)


Almost every modern use of the word decimate is in this expanded sense. However, Merriam-Webster, Dictionary.com, The Free Dictionary, and Oxford Dictionaries all list the historical “destroy a tenth” definition along with the modern definition, and it’s not uncommon for people to argue that this is the only definition that should be allowed for the word--even though the word in that sense is rarely, if ever, used (The British National Corpus gives 23 results for decimate, 21 of them using the modern definition and the remaining two complaining about the use of the modern definition).

However, there are plenty of other words whose definitions have been expanded beyond their original number-specific etymologies, such as alternative and combine, and you don’t see anyone causing a stink about those. Is there a reason why people want to cling so desperately to decimate’s literal definition? What’s the point of trying to enforce a definition that no longer has any de facto existence?

EDIT: Some people asked for examples of people complaining about decimate being used with the expanded definition rather than the historical one. Here are some examples:

This website lists using decimate in this way as an error.

This Oxford Dictionaries blog addresses the "linguistic pet peeve" of people who complain about decimate being used this way.

This NPR article quotes the senior supervising producer of their Arts & Life section, who says,

"I think the people who defend the original meaning of 'decimate' do so in part because we feel it's sad to lose a word for describing something so precisely and in a way that evokes such history. I guess one can substitute 'collective punishment' or 'culling.' But every time we let word meanings bleed together, it's like a little star winking out."

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    People need something to complain about. And there aren't nearly enough real problems in the world to suit some people. – Hot Licks Feb 18 '15 at 22:06
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    I suspect it's because the root dec is still used to refer to 10 in so many other words, so the link is very obvious. There's no such recognizable root in alternative and combine. – Barmar Feb 18 '15 at 22:06
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    But the root bi is still used to refer to 2 in many other words, too, so how did combine get its meaning expanded without complaint? – Nicole Feb 18 '15 at 22:07
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    Many of us get annoyed when linguistic drift spoils a useful tool - when my son uses my best chisel as a can-opener, for instance, or Microsoft randomly changes the Word interface. There's not much to be done about it, but it's cathartic to rant. – StoneyB on hiatus Feb 18 '15 at 23:10
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    Not just practically useless. I'm not aware of any military units being decimated in the last, oh, 1500 years or so, although I may be mistaken. While the phrase might well be applied to, for instance, civilian populations which provided hostages to the Third Reich as protection against insurgent activities, I'm pretty sure the exact 1 of 10 ratio was not observed - so the example fails. There's an excellent critique of the issue here blog.oxforddictionaries.com/2012/09/…, and it's entirely possible that the pedants have the wrong of it. – WhatRoughBeast Feb 19 '15 at 22:13

Actually, decimate isn't the only word linked to its number-related root. You will still find people who, for example, mentally connect hecatomb with the sacrifice of 100 oxen, myriad with the number 10,000, and millennarianism with 1000 years in Christian eschatology. I'm one of them.

To me, these connections don't provide a compelling reason to banish use of any of these terms in nonnumerical settings, but they do enrich my sense of where the words came from and perhaps hint at how they came to be applied in the situations in which they are commonly used today.

Ultimately, etymology doesn't provide a persuasive basis for denying the legitimacy of the way people use words today when it departs from the way people used them decades or centuries ago. But words do have a past, and getting annoyed when people bring up that past seems to me no more productive or sensible than getting annoyed about the fact that meanings evolve.

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    This is all true—but while I've seen many argue out of misguided pedantry that decimate should never be used in the extended sense, I've never seen anyone argue that hecatomb should never be used to refer to anything but the sacrificial slaughtering of exactly 100 oxen, nor even that myriad should only be used to mean exactly 10,000. And I've certainly never seen anyone complain that what they were drinking should not be called a fruit punch because it doesn't contain exactly five ingredients. So the question remains: why are people so hung up on decimate in particular? – Janus Bahs Jacquet Feb 20 '15 at 9:52
  • @Janus: I think Barmer's comment above helps explain the phenomenon. Decimate looks so much like decimal that many people with a not-very-deep awareness of etymology (certainly not deep enough to notice the bi component of combine) make the connection between deci and "one-tenth." Many people think of pedantry as the preserve of academics, but I think it exists on a continuum that ranges far into popular culture—and the greater the number of amateurs (like me) who know some stray fact, the more likely that fact is to become a point of pride (and pedantic insistence) to glorify. – Sven Yargs Feb 20 '15 at 16:41
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    Perhaps I'm just a bit wary of that explanation because I personally (even as someone who dedicates a great deal of my life to etymology) never made any connection between decimate and decimal at all until I learned of the original (and never-used) meaning. I had always intuitively parsed it as de-cimate, without really thinking much about what *cimate might be (but possibly grouping it mentally with incinerate, etc.). Then again, that's anecdotal and it may be just me. – Janus Bahs Jacquet Feb 20 '15 at 16:44
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    Your wariness is surely justified. In my experience, people rarely complain that December ought to be renamed because it is no longer the tenth month of the year, so the explanation for pedantic enthusiasm over decimate can't be that the "Uphold the Purity of Deci-" lobby is unusually strong and equally active on all fronts. But that doesn't prove anything about a decimate/decimal connection. My position is simply that I haven't seen an explanation (or even a suggestion) that seems more plausible than Barmar's. – Sven Yargs Feb 20 '15 at 17:11

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