Q: I just caught up with your Thanksgiving post on the names for turkey parts. How about something on the names for people parts? I was recently surprised to learn that the meanings of “arm” and “leg” in anatomy differ from common usage.
A: This was news to us too, but then we skipped anatomy class. You’re right, though. “Arm” and “leg” have special meanings in medicine.
In standard anatomical terminology, the word “arm” means what most of us think of as the upper arm—the part between the shoulder and the elbow.
And the word “leg” in anatomy means what most of us think of as the lower leg—between the knee and the ankle.
The limbs as a whole are called the “upper limb” and the “lower limb.”
We quizzed our own doctor about this as she was giving us our annual physicals the other day. She said physicians call the upper arm the “arm” or the “brachium”; the part below the elbow is the “forearm” or the “antebrachium.”
Why? Because a doctor is generally concerned with one part of a limb, not the limb as a whole. And the parts are distinct—different bones, different muscles, and so on.
Hence, different terminology. The words “arm” and “leg” as used in the general sense would be too broad for medical purposes.
Kenneth Saladin’s book Human Anatomy (2007) has this explanation:
“The upper limb is divided into brachium (arm proper), antebrachium (forearm), carpus (wrist), manus (hand), and digits (fingers); the lower limb is divided into thigh, crus (leg proper), tarsus (ankle), pes (foot), and digits (toes).”
Elsewhere, Saladin explains that the term “arm proper” means the upper arm, which “extends from shoulder to elbow,” while the “leg proper” is “below the knee.”
Another medical textbook, Grant’s Dissector (2012), by Patrick W. Tank, says, “The upper limb is divided into four regions: shoulder, arm (brachium), forearm (antebrachium), and hand (manus).”
Earlier, Tank writes: “The lower limb is divided into four parts: hip, thigh, leg, and foot. It is worth noting that the term leg refers only to the portion of the lower limb between the knee and the ankle, not to the entire lower limb.”
Tank is right—this IS worth noting, since in ordinary language the words “arm” and “leg” are interpreted less narrowly.
The Oxford English Dictionary defines “arm” (the body part, that is) only in the usual sense: “The upper limb of the human body, from the shoulder to the hand.”
There’s no mention in the OED of a medical definition of “arm” that would differ from that one.
Oxford adds that “the part from the elbow to the hand” is known as “the fore-arm.” Elsewhere, it defines the “forearm” as “the part of the arm between the elbow and the wrist; sometimes the whole arm below the elbow.”
On the other hand (if that’s the appropriate expression), the OED’s definition of a person’s “leg” includes the ordinary sense of the word as well as a more restrictive sense.
Here’s the definition: “one of the two lower limbs of the human body; in narrower sense, the part of the limb between the knee and foot.”
It’s interesting to note that while people have “forearms,” they don’t have “forelegs,” a term used only of animals. The OED says a “foreleg” is “one of the front legs of a quadruped.”
We can’t end this without mentioning “an arm and a leg,” which Oxford describes as a colloquial expression meaning “an enormous amount of money, an exorbitant price; freq. in to cost an arm and a leg.”
The OED’s first citation is from Lady Sings the Blues, the 1956 autobiography of one of our favorite singers, Billie Holliday, written with William Dufty: “Finally she found someone who sold her some stuff for an arm and a leg.”
Check out our books about the English language