Why Is 'Chiropractic' Singular?

Hi, Mignon. Long-time listener. First-time caller. I have been curious for a long time about the word 'chiropractic' because of how it's a noun like 'mathematics,' or 'physics,' or 'therapeutics,' but it's singular as a noun. I think it is singular, and that it is one of the few nouns that end in S and it's a singular noun. So I don't know. That's my question: Why is not 'chiropractics?'

It had never occurred to me that "chiropractic" is a singular noun, but you're right. The abbreviation "D.C." you see after a chiropractor's name stands for "doctor of chiropractic." Not "chiropractics" or "chiropractic medicine," but just "chiropractic."

According to Etymonline, the noun "chiropractic" was coined by Americans in 1899. It's a combination of two Greek roots: "chiro," which means "hand" and "pratikos," which means "practical." Chiropractors use their hands to manipulate your body, so the name makes sense.

And it is odd that it's singular. Aside from the fact that the second root, "pratikos," ends with an S, many other disciplines end with "-ics": physics, pediatrics, mathematics, linguistics, economics, ethics, and so on.

There are many nouns that end in just "-ic" too though. The Oxford English Dictionary highlights a few disciplines such as "music," "arithmetic," and "rhetoric." 

Usually, these words we borrowed from Greek started out as adjectives, and you'll recognize the "-ic" suffix in adjectives like "diabolic," "sophomoric," and "platonic."

The most interesting point is that when these words moved from Greek to Latin, sometimes they were treated as singular and sometimes they were treated as plural. The OED says, "There was in medieval Latin considerable fluctuation in the grammatical treatment of these words." In Italian, Spanish, and German, they were "regularly treated as feminine singular." The same was true of French, but again according to the OED, "in French, from the 16th century, [they were sometimes treated] as plural (as in 'les mathématiques')."

In English, there's a dividing line in the middle of the 16th century. Before then, these kinds of words were generally treated as singular, and tended to be written like the French words: for example, "mathematique," "mechanique," and "economique."

But after the middle of the 16th century, some, including the names of sciences...

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