Yes, "pleural" is one of those medical words, like "lumbar" that sometimes sneak into my nonmedical writing. Misplacing "plural" with "pleural" is a dead giveaway that the writer commonly uses medical language. (That might be a neat clue in a mystery story, by the way.)
The issue of plurals in medicine is complicated by the fact that the language of medicine derives from several different original languages, Greek and Latin being the most common. I studied Latin in high school, so that helps me a little, but Greek is ... well, Greek to me. So are Arabic, Chinese, Dutch, Persian and many of the other source languages for medical terminology. Although some understanding of the rules of plural formation is helpful, most of us learn our medical plurals one word at a time.
Today, English has become the new international language of medicine, just as Latin was for many centuries previously. (Physicians in the 18th century, for example, conversed in Latin on a regular basis.)
For a fascinating capsule summary of the linguistics of medicine, check out www.jrsm.org/cgi/content/full/97/4/187 .
It seems that many terms of Greek origin simply follow English rules. For example, "bradycardia" (from Greek words for "slow" and "heart") would become "bradycardias." On the other hand, words from Latin tend to follow the rules from that language, although some modernization is always ongoing: "cannulae" is the Latin plural of "cannula," but we often use the anglicized "cannulas," in clinical narratives.
Confusion can occur among English speakers about which word form is plural and which is singular. For example, "diverticula" is sometimes used as a singular form and, by analogy with words like "sclera" (a singular), the speaker forms the incorrect plural "diverticulae." In reality, of course, "diverticulum" is the correct singular form, and "diverticula" is the plural. The word "nares" seems to offer particular difficulties. It is assumed to be plural, which it is, but then the speaker wants to use "nare" as the singular (following simple English rules). The correct singular (based on Latin rules) is "naris."
Another confusing term is "vas deferens": the plural is "vasa deferentia." And what about "scissors"? A quick survey of dictionaries suggests that this is a word that can be used with either singular or plural verb forms but, as a noun, it has no true singular form. That is, the surgeon uses one Metzenbaum scissors, not "scissor." If the busy surgeon uses more than one of these implements, they are still "scissors," although the plural could be indicated by saying (wordily), "two pairs of scissors."
Finally, consider the term "corpus cavernosum." If you want to talk about more than one of these anatomical features, you will use "corpora cavernosa." I've encountered in dictation the sentence, "Two vertical stay sutures were placed into each corpora." The correct word here is "corpus," because the dictator clearly means one, as shown by the use of the word "each."
Happy 2008, and remember: don't run with that scissors, because you might slip and slice your naris!
Rebecca A. McSwain is currently working as a production MT for a national service. She has worked as an MT supervisor, business owner, instructor and QA manager. She's a member of AHDI and the American Medical Writers Association. She has a PhD in anthropology and continues to work on anthro-related writing projects in her spare time. She can be reached at email@example.com .