Turn, turn, turn.

Dear Word Detective: I have been bothered lately by this idea: I can be inverted, converted, introverted, extroverted, averted, diverted, subverted, and of course the ever-popular perverted. What I can’t be is “verted.” Can you explain the origin of this strange word that apparently doesn’t exist without a prefix? — Vic Walton.

Speaking as someone usually considered an introvert, I find your flexibility impressive. I’ve tried being an extrovert a few times, but people tend to back away slowly and the conversation dies. As for perversions, it occurred to me the other day that I was 18 years old before I saw somebody put ketchup on french fries. Seriously.

As a matter of fact, you can be “verted.” More importantly, you can “vert,” which is a somewhat obscure verb meaning “to turn in a particular direction” most often used today in medical contexts (“All of the muscles of the eyes may be relatively weak. The ducting or verting power is not as great as it should be,” 1903).

More to the point, all the words you mentioned, and many more, share a common root — the Latin verb “vertere,” meaning “to turn or overturn.” There are dozens of descendants of “vertere” in modern English, most of which retain at least the hint of the basic idea of “turning,” although in some cases the connection has become tenuous over the centuries (as in “vertebrae,” so named because they serve as the axis on which the human body can be turned).

To “invert” something, for instance, is usually to turn it upside down, but the original meaning was to turn it “in,” i.e., inside out. In common usage today, “to invert” means to reverse the relative positions of things. “Convert,” from the Latin form “convertere” (literally “to turn together”), was originally used in English in the religious sense of “to cause to turn to and embrace a religious faith,” only later taking on the more general meaning of “change” or “transform” we use speaking of “convertible” cars. An “introvert” is someone who is withdrawn and “turned inward” (“intro” meaning “inward”), while an “extrovert” loves to be around other people. To “divert” was originally “to turn aside,” which also gave us “diverse” (now meaning “varied,” but originally “turned different ways”) as well as “diversion,” something that turns us away from our previous course.

When we “subvert” (“sub” meaning “under”) something, we undermine or destroy the foundation or basis of that thing, as if we were turning it over from underneath. When “subvert” first appeared in English in the 14th century, it meant to literally destroy something (a building, a city) down to the ground. But within a few years “subvert” was being used to mean the destruction and overthrow of institutions and political systems.

“Pervert” continues the “turning” theme of the other “vert” words, but appends “per,” a Latin prefix meaning, in this case, “away, toward the bad” (also found in “perish” and “perdition”). To “pervert” something is to turn it away from the proper or correct path, to corrupt it, and a “pervert” (the noun) is a person who has been led astray.