The whole comprises its parts: "the book comprises twelve chapters." The parts compose the whole: "twelve chapters compose the book" — or, more naturally, "the book is composed of twelve chapters." The error to know is "comprised of", which mixes the two.
The core difference
The direction is the whole difference, and it runs opposite ways.
- comprise — the WHOLE comprises the parts. Never takes "of".
- compose — the PARTS compose the whole; the whole is composed of parts.
Why "comprised of" is objected to
Because comprise already means "consist of", so adding of is redundant twice over. "The team is comprised of five members" should be either "comprises five members" or "is composed of five members". The construction is extremely common and many dictionaries now record it, so it is not a hanging offence — but it is one of the small number of usage points editors reliably catch.
The reliable check
Substitute consists of. If it fits, you want comprises without the of, because comprises already contains it.
Frequently asked questions
Is "comprised of" wrong?
It is widely used and now recorded in dictionaries, but usage guides object because comprise already means "consist of", making the "of" redundant. Editors reliably change it.
What is the correct construction?
Either "the whole comprises the parts" or "the whole is composed of the parts".
How do I check which to use?
Substitute "consists of". If that works, use comprises — with no "of" after it.