Note: If you are not a grammar geek, you may want to skip to the closing paragraphs (“Given the plethora…”).
This verb is mutilated in so many ways it should be excised from the language altogether. Here are the two most common ways in which it is misused:
“The U.S. is comprised of fifty states,” and “Fifty states comprise the U.S.” (We’ll set aside Puerto Rico for the sake of brevity here.)
The point of confusion lies in the fact that when the active voice of the verb is used, its definition can be expressed in passive voice or active, and when the passive voice is used, the verb’s definition can be expressed in active voice or passive. To wit:
“Comprises” literally means “embraces” or “encloses,” but you could define it in passive voice as “is made up solely of” or “is composed solely of.” You could safely substitute “includes,” “contains,” or “consists of,” as long as you tag on “and nothing else” at the end.
Here are the examples cited above, corrected:
Active voice: “The U.S. comprises fifty states.” (That is, “The U.S. is made up solely of (passive voice) / is composed solely of (passive) / contains (active) fifty states and nothing else.”)
Passive voice: “Fifty states are comprised in the U.S.” (That is, “Fifty states and nothing else make up (active voice) / constitute (active) / are included in (passive) / are embraced by (passive) the U.S.”)
Further examples: “His harem comprises three wives and fourteen concubines.” “The orchestra comprises 150 musicians, their instruments, and a conductor.”
If you put “comprise” into passive voice, always say “comprised in,” e.g., “The parts are comprised in the whole”; that is to say, “The parts make up / constitute / are included in / are contained in the whole.”
Here is an even nit-pickier point: The difference between “comprises” and “includes” lies in whether there are other parts in the whole besides those listed; if there are other parts of the whole that are not listed, use “include”; if the parts listed make up the entirety of the whole, use comprise.
For example, “The U.S. military includes (not comprises) the Army and the Navy.” Here you would use “includes” because the Marines and several other branches of the armed forces are also part of the military, but they are not listed here. If you did list them all, you would use “comprises” instead: “The U.S. military comprises the Army, the Navy, the Marines, the Air Force, etc., etc., etc.”
Given the plethora of alternatives, it would be better just to drop the damned thing from the dictionary and be done with it. However, as long as there are politicians and wanna-be scholars who feel compelled to impress people with the occasional fancy word (mine is bigger than yours), but are too lazy to take the time to bone up - you should pardon the pun - on the finer points of its usage, people will continue to trot out “comprises” at the wrong time, in the wrong place, and in the wrong way.
I have become so pessimistic with regard to the current state of the written and spoken word these days that it takes very little to make me rejoice. I once placed a business call and asked to speak with a specific person; when the gentleman who answered the phone said, “This is he,” I almost French-kissed the handset.
Whenever I come across an author (usually a dead one, unfortunately) who uses “more important” instead of “more importantly,” and correctly employs “to matriculate” and “to comprise,” I get so excited, I say “Yay!” and do a little happy dance.
P.S. I did see “matriculate” used correctly by Walter Isaacson in his biography of Steve Jobs, and yes, I did the little happy dance.