Comprise and Compose . . . Which Is Which?

As editors, we see a lot of confusion between comprise and compose. And, honestly, whenever it comes up, we frequently have to reach for our Chicago manuals for a little grammar refresher. We hope this post will help us all keep the two straight!

Comprise and compose are similar words, both in spelling and meaning. We know they both have some connection to "contain," but the two words aren't interchangeable. Here's a tip for figuring out which is which: think of comprise as "contains" and compose as "is contained in." Let's try some examples:

• The group comprised 3 girls and 4 boys.
• Several new laws comprised the bill.

Now let's try to replace "comprise" with the cheat word "contains":

• The group contains 3 girls and 4 boys.
• Several new laws contained the bill.

So one of those works, and one of them doesn't. Let's try putting "composed" in the place of "comprised" using the cheat words "is contained in":

•  Several new laws are contained in the bill.

Ah, much better! "Several new laws compose the bill."

Basically, it's a "parts vs. whole" situation. In your sentence, which one is the part, and which is the whole? I like to think of it this way: the book (whole) comprises its chapters (parts), and the chapters (parts) compose the book (whole).

Now, it can get tricky because you could replace "comprises" with "is composed of" so it would say "the book is composed of its chapters." This is perfectly valid; however, make sure you never use "is comprised of." Think about it: "is contained of" doesn't sound right. That's because it's not! Remember to distinguish which is the "part" and which is the "whole," and make the necessary change.

Finally, let's take a look at what the 16th edition Chicago Manual of Style has to say about comprise vs. compose (5.220):

Use these with care. To comprise is "to be made up of, to include" {the whole comprises the parts}. To compose is "to make up, to form the substance of something" {the parts compose the whole}. The phrase comprised of, though increasingly common, is poor usage. Instead, use composed of, consisting of, or made up of.

So there you have it! If you have any problematic phrases you want to throw our way, list them in the comments and we'll help you out.