comprise vs. compose
Most people who get this wrong write "is comprised of", and they are in enormous company. It is so widespread that several major dictionaries now list it without comment. Careful editors still treat it as an error. Which puts you in the odd position of following a rule that is losing, in front of readers who may be the last people enforcing it.
comprise
A verb. To consist of, or be made up of. The whole comprises the parts — and it is never followed by "of."
- The committee comprises nine members.
- The portfolio comprises equities and bonds.
- The building comprises four floors and a basement.
- Not "is comprised of nine members" — the construction most style guides still reject.
compose
A verb. To make up or constitute. The parts compose the whole, and "is composed of" is correct.
- Nine members compose the committee.
- Equities and bonds compose the portfolio.
- The committee is composed of nine members.
- Water is composed of hydrogen and oxygen.
Why comprise and compose get mixed up
Compose and comprise describe the same relationship between a whole and its parts, but from opposite directions. The whole comprises the parts: the committee comprises five members. The parts compose the whole: five members compose the committee. You can also say the whole is composed of its parts.
The phrase that causes trouble is "comprised of". It has become very common, and some dictionaries now accept it, but many editors and careful readers still treat it as a mistake, because comprise already means "is made up of". Adding "of" says it twice.
If you want to avoid the argument, there are safe alternatives that everyone accepts: consists of, is made up of, and is composed of. And never follow comprises with of.
Common mistakes
The committee is comprised of five members.
✓The committee is composed of five members.
"Comprised of" is widely criticized. Use "is composed of", "consists of", or simply "the committee comprises five members".
Five members comprise the committee.
✓Five members compose the committee.
The parts compose (or make up) the whole; only the whole comprises.
The kit comprises of a tent, stove and lantern.
✓The kit comprises a tent, stove and lantern.
Comprise already includes the meaning of "of", so it takes a direct list.
Quick way to remember
Put the whole first and use "comprises" with no "of." Put the parts first and use "compose," or turn it round as "is composed of." If you find yourself typing "is comprised of," swap in "is composed of" or "comprises" and the sentence is safe.
Questions
Is "comprised of" ever acceptable?
It is common in everyday writing and listed in some dictionaries, but it still draws objections in formal and professional writing. "Consists of" says the same thing with no risk.
Where does constitute fit in?
It works like compose: the parts constitute the whole. "Women constitute half the workforce."