Suppose a friend said to you, “I know you’re disinterested, so I want to ask you a question presently.” Then he didn’t say anything. Would you be momentarily nonplussed?

Quite likely, yes. The above paragraph contains four words whose primary definitions have changed or are currently changing. Disinterested traditionally meant “impartial,” and now is generally used to mean “uninterested.” Presently has gone from “shortly” to “currently”; momentarily from “for a moment” to “in a moment”; and nonplussed from perplexed to unimpressed, or fazed to unfazed. To lend support to my theory that the new meanings now dominate popular usage, I gave an ungraded and anonymous quiz to one of my college classes—an advanced writing seminar. Here is the percentage who gave the “wrong”/new definition:

Disinterested: 94

Momentarily: 88

Presently: 88

Nonplussed: 80

We all know that words change their meanings all the time, sometimes glacially (the prescriptivists have long been fighting on behalf of the “impartial” sense of disinterested) sometimes relatively quickly (that nonplussed thing snuck up on me). * But this fact raises a question (it doesn’t beg the question—that means something else): How long should we hold on to a word’s old meaning?

This is a subset of the larger issue—an ethical one, really—of how we should deploy our language knowledge. Some people—often children of English teachers or Anglophiles—proudly wear their knowledge on their sleeve, and adopt hypercorrect linguistic behavior. Take Ray Magliozzi, the less laughter-prone of NPR’s Car Talk guys, who turns his sentences into pretzels so as to avoid ending them with prepositions: a “rule” that has been out of favor for roughly half a century. (Ray consequently favors the phrase “with which.”) I actually heard him use the word “shall” on last week’s show. A subclass of this group favors ur-renditions of common expressions. Adopting the diction of George Gissing or Walter Pater, they will choose stamping (instead of stomping) grounds, champing (instead of chomping) at the bit, pompons (instead of pompoms), or titbits (instead of tidbits). * Such archaism seems designed to attract attention, and nothing more.

But using a meaning on its way to extinction can be nobler than such exhibitionism. Balancing the possibility that you’ll confuse your audience, and the prospect of appearing pretentious or dorky, is the chance that the old meaning could be a really good meaning, which no other word conveys precisely. There is no exact synonym for (the old-fashioned) disinterested, for example. In such cases, keeping a “legacy” sense in circulation is laudable activism in pursuit of semantic sustainability—as if you found some members of a near-extinct species of mollusk and built a welcoming environment in which they could breed.

So, pedantry on one side, conservation on the other. What’s needed is an algorithm to help you decide where on the continuum a particular word or expression lies.

Guess what: I have such an algorithm! Or, more precisely, I have a somewhat arbitrary metric. In the chart below, the number under the percent sign indicates the proportion of the first 20 hits on a Google News search reflecting a word’s oldmeaning. The “utility rating” is my view of how valuable that old meaning is. Lion’s share gets a 0 because it is a cliché and one can express the traditional meaning simply by saying all. Fortuitous gets a 2 because accidental or coincidental mean pretty much, though not exactly, the same thing. Disinterested gets a 3.

To get the score, I took the percentage of Google hits that used the old meanings and added the utility ratings: 20 points for 1, 40 for 2, and 60 for 3. The final score correlates roughly with academic grades. That is, 65 or better means the old sense still passes, and you should feel free to use it. If it doesn’t pass, you can either convert to the new sense or, if that’s too painful, avoid the word entirely.

If you are champing at the bit to decimate me, be ready, because I will be done presently.

Word Traditional Definition New Definition(s) % Utility Rating Score Beg the question Assume a claim is true without evidence other than the claim itself (circular logic) Prompt or raise a question 5% 3 65 Decimate Kill one-tenth of a population Kill or eliminate a large enough proportion of something so as to render it ineffective 0% 0 0 Disinterested Lacking a selfish reason to favor a particular side in a debate or contest, and therefore impartial Uninterested 15% 3 75 Eke out Make a small amount of something last, with sparing use Achieve narrowly and laboriously 0% 3 60 Fortuitous Accidental; unplanned Lucky 5% 2 45 Fulsome Offensively excessive Abundant; full 0% 2 40 Hoi polloi 1 The common people The fancy people 2 90% 3 1 110 Lion’s share All or nearly all The majority 0% 0 0 Momentarily For a moment In a moment; presently 80% 4 1 100 Nonplussed Perplexed Unfazed; nonchalant 45% 2 85 Presently Shortly Now; currently 0% 2 5 60 6 Toothsome Delectable; attractive Having big or prominent teeth; quality of a food that is dense or chewy 30% 2 70 Verbal In words Oral; spoken 0% 2 40 1 Pedants and classics majors will point out that it is incorrect to say “the hoi polloi,” because in Greek, hoi means the. 2 Probably because it sounds like “hoity toity.” 3 I did not include two articles that discussed the proper meaning of hoi polloi. 4 This is a misleadingly low number, I would say, since the new meaning of momentarily is most often used conversationally, and hence is not likely to show up in news reports. Most of the Google News new-meaning citations are real-time updates, for example, “More details will be added to this story momentarily.” 5 The new meaning of momentarily denotes the traditional meaning of presently. 6 I have made an executive decision to raise the score of presently by twenty points because context makes clear that the traditional meaning indicates a future action or occurrence, reducing confusion or ambiguity.

Update, April 8, 2011: As a reader identifying himself or herself as Jamougha has correctly pointed out, the use of disinterested to mean “uninterested” is not “new,” and I was being imprecise to call it that. It goes back to the 17th century—as does using the word to mean “impartial” or “neutral,” which I equally imprecisely described as “traditional.” There’s a similar history to presently. The Oxford English Dictionary cites uses to mean both “in a little while” (which I called “traditional”) and “now” (which I called “new”) back to the 15th century.

Here is a more precise account. Around the middle of the 20th century—not coincidentally, the time when the lion’s share of present-day language prescriptivists were developing their prescriptivism—a consensus developed about various “rules” and meanings, including disinterested and presently. A key text reflecting that consensus is the second edition of H.M. Fowler’s A Dictionary of Modern English Usage, which was published in 1965 and was the work of Sir Ernest Gowers. Gowers defines disinterested as “free from personal bias.” He notes that OED called the “uninterested” sense “obsolete” until a 1933 edition, when it removed the designation, and says “this revival has since gathered strength.” Sir Ernest did not approve, concluding, “A valuable differentiation is thus in need of rescue, if it is not too late.”

As for presently-to-mean-“currently,” the usage note in the current edition of the OED is a noncommittal model of its kind: “Apparently avoided in literary use between the 17th and 20th centuries, but in regular use in most English dialects and by Scottish writers; revived in the 20th cent. in the U.S., subsequently in Britain and elsewhere. Regarded by some usage writers, esp. after the mid 20th cent., as erroneous or ambiguous.” Sir Ernest, predictably, raised an eyebrow at this use, commenting, “It is now enjoying a vigorous revival, though whether for any better reason than novelty hunting may be doubted, seeing that we have available for the same purpose not only now but also for those who dislike monosyllables at present and currently.”

The history of both words illustrates the truth that, when it comes to language, there is no right or wrong in a metaphysical sense, only a consensus that holds for a particular period of time. And hold your comments: by consensus I mean the “new” sense of “general agreement,” not the “traditional” sense of “unanimous agreement”!

Correction, April 8, 2011: This article originally stated that prescriptivists have been fighting on behalf of the “original” sense of disinterested (meaning “impartial”) for centuries. Actually the fight’s been going on since about the middle of the 20th, and it’s not quite accurate to call “impartial” the “original” sense of disinterested for reasons outlined in the update. ( Return to the corrected sentence.)

Correction, April 7, 2011: Because of an editing error, this article originally stated that pompon was an alteration of pompom, rather than vice versa. “Pompon” is the hypercorrect word. (Return to the corrected sentence.)