Wikipedia cofounder Jimmy Wales at a news conference before the London Wikimania conference in 2014. Carl Court/Getty Images "A substance comprised of pigments suspended in a carrier is paint."

Can you spot the mistake in the above sentence?

Answer: It's the use of the term "comprised of." It's a conflation of "comprised" and "composed of," and it's not technically correct. The sentence should say, "A substance consisting of pigments suspended in a carrier is paint." (Or, more clumsily, "Paint comprises pigments suspended in a carrier.")

"Comprised of" is in common usage, however, and most people don't realise it's wrong. But Bryan Henderson is on a mission to change that. Backchannel reports that the 51-year-old software engineer is an extraordinarily active contributor to Wikipedia, making 47,000 edits over the past decade — almost exclusively to correct other editors' incorrect usage of "comprised of."

Henderson told Backchannel that when he made his first edits "and nobody came back and scolded me for it," he was hooked. He initially identified 15,000 incorrect uses of the term using Google and began methodically working through them. There was a backlash from editors, which "came as quite a surprise," as other Wikipedia users were irked to be corrected on a mistake they didn't realise they had made.

But Henderson persevered, and he wrote scripts that would hunt down uses of the term and flag them for him to correct. He has now corrected every single misuse of "comprised of" on English-language Wikipedia — no mean feat, considering the site has more than 4.7 million articles. Nonetheless, between 70 and 80 new ones appear on the site each week, according to Backchannel, and Henderson spends about an hour every Sunday night hunting them down.

He has even inspired his brother to take up a similar cause. Robin Henderson now keeps an eye out for the incorrect term "based around" (it should be "based on") on Wikipedia — though he says he doesn't have the same "search and destroy" attitude as Bryan.

Henderson (who lives in San Jose, California) has also written extensively on "comprised of," justifying his actions with a 6,000-word mission statement on his user page. Here some of the reasons — in his words — "comprised of" is "poor writing":

It's completely unnecessary. There are many other ways to say what the writer means by "comprised of." It adds nothing to the language.

It's illogical for a word to mean two opposite things.

The etymology of the word does not support "comprised of." It comes from Latin words meaning to hold or grasp together. Other English words based on those same roots are "comprehensive" and "prehensile" (as in a monkey's prehensile tail; it can grab things). Comprise's French cousin also makes this clear.

It's new. Many Wikipedia readers learned to write at a time when no respectable dictionary endorsed "comprised of" in any way. It was barely ever used before 1970. Even now, style manuals frequently call out this particular usage as something not to do.

It's imprecise. English has a variety of ways to say things the writer means by "comprised of." "Composed of," "consists of," and "comprises" are subtly different. It often takes careful thought to decide just which one of these things the article should say. Thus the sentence with "comprised of" isn't quite as expressive.

Many writers use this phrase to aggrandise a sentence — to intentionally make it longer and more sophisticated. In these, a simple "of," "is," or "have" often produces a sentence that is easier to read (Example: "A team comprised of scientists" versus "a team of scientists").

In Wikipedia parlance, Henderson — editing under the user name Giraffedata — is a "WikiGnome." It's a type of editor who is happy to "make useful incremental edits without clamouring for attention," according to the Wiki page on them. He has received numerous accolades from the community for his work.

He writes that he doesn't edit Wikipedia "for personal taste" — it's because "the fact that lots of other people feel the same way is what makes it seem like a good edit to me."

"If I can spare any readers [the] discomfort [of seeing it] without hurting anyone else, why wouldn't I?"