“Compose” and “Comprise”: What’s the Difference?

There are plenty of English words that get mixed up all the time, like lay and lie, ensure and insure, compliment and complement, etc. Now, it’s time to talk about compose and comprise!

Both compose and comprise have to do with parts making up a whole, but one of them goes with the whole and the other goes with the parts. You’ll see what I mean.

What’s the Difference?

Compose means “to form by putting together.” A good synonym for compose is “constitute” or “make up.” The PARTS compose the WHOLE.

Comprise means “to be made up of.” A good synonym for comprise is “include.” The WHOLE comprises the PARTS.

The whole comprises the parts, and the parts compose the whole. You could also reverse these statements and say that the parts are comprised in the whole and the whole is composed of its parts.

This might all sound a bit confusing, but there’s a pretty decent trick you can use to keep the words straight.

The Trick

Swap out comprise or compose with their synonyms to find out which one is correct:

• Comprise can be substituted with include
• Compose can be substituted with make up

There are a couple of caveats you must remember with this trick:

1. Make sure to adjust the tense to match (e.g., if the sentence uses the past tense “comprised,” use the past tense “included”).
2. Keep ALL other words when you substitute comprise or compose. If your sentence says “The whole is composed of its parts,” KEEP “is” and “of”: “The whole is made up of its parts.”

CORRECT: The whole comprises the parts. = The whole includes the parts.

CORRECT: The parts compose the whole. = The parts make up the whole.

CORRECT: The parts are comprised in the whole. = The parts are included in the whole.

CORRECT: The whole is composed of its parts. = The whole is made up of its parts.

If you have the wrong word, the matching synonym will not make sense in your sentence.

INCORRECT: The whole composes the parts. = The whole makes up the parts.

This isn’t true: it’s the parts that make up the whole. The correct word here, then, should be comprises.

INCORRECT: The parts comprise the whole. = The parts include the whole.

Once again, this statement is false: The whole includes the parts, not the other way around. The correct word here, then, should be compose.

INCORRECT: The parts are composed in the whole. = The parts are made up in the whole.

INCORRECT: The whole is comprised of its parts. = The whole is included of its parts.

One thing that really helps me is to keep this list handy and use it to check my work:

• The whole comprises the parts.
• The parts are comprised in the whole.
• The whole is composed of its parts.
• The parts compose the whole.

When I’m not sure about a sentence, I check it against that guide; if it fits, then I know I’ve got the correct word.

For example, let’s take this sentence: Kentucky is composed of 120 counties.

I find the sentence in the list that uses “is composed of” (the 3rd bullet point) to match the one in my sentence. Then, I check to see if the rest of the sentence matches.

The whole is composed of its parts = Kentucky is composed of 120 counties.

Kentucky is “the whole” and 120 counties are “its parts,” so this sentence checks out! “Is composed of” is correct.

Examples

The parts: fifty states / The whole: the United States of America

• Fifty states compose the United States of America.
  • The parts (fifty states) make up (compose) the whole (the USA).
• The United States of America comprises fifty states.
  • The whole (USA) includes (comprises) the parts (fifty states).

The parts: two acts / The whole: the play

CORRECT: The play is composed of two acts. OR The play comprises two acts.

INCORRECT: The play is comprised of two acts. NOR The play composes two acts.

The parts: 500 pieces / The whole: the puzzle

CORRECT: The puzzle is composed of 500 pieces. OR The puzzle comprises 500 pieces.

INCORRECT: The puzzle is comprised of 500 pieces. NOR The puzzle composes 500 pieces.

Let’s swap and start our sentence with the parts (500 pieces).

CORRECT: 500 pieces compose the puzzle. OR 500 pieces are comprised in the puzzle.

INCORRECT: 500 pieces comprise the puzzle. NOR 500 pieces are composed of the puzzle.

Do We Really Need To Know This?

When writing something formal or professional (such as an essay for school or a business document), you should definitely be sure to use the right word. The Merriam-Webster Dictionary of English Usage cautions against mixing up compose and comprise, as the mistake could cost you your credibility as a writer.

If you just can’t seem to keep these words straight, you can choose to avoid them both and instead go with one of their synonyms (include or make up, depending on the context).

What questions do you have about comprise and compose? Let me know in the comments!

Click here to learn the difference between lay and lie!

Sources:

• “America’s Most Trusted Dictionary.” Merriam-Webster. Accessed August 7, 2024. https://www.merriam-webster.com/.
• Ebbitt, D. R., and W. R. Ebbitt. Index to English. 8th ed. New York: Oxford University Press, 1990.
• Einsohn, Amy. The Copyeditor’s Handbook. 3rd ed. Berkeley and Los Angeles, California: Univ of California Pr, 2011.