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The Meaning of “Comprise”
It seems simple enough: “to comprise” means “to contain” (1), as in “The house comprises seven rooms.” In other words, this house has or contains seven rooms. When you use “comprise,” you’re talking about all the parts that make up something. Usually. More on that a little later.
The important thing to remember when you’re using the word “comprise” is that the item that is the whole shebang comes first in the sentence; second come the items that are its parts. For example, you might say, “A full pack comprises 52 cards.” The pack is the whole shebang, so it comes first in the sentence. It would be wrong to say, “Fifty-two cards comprise a full pack.” Likewise, America comprises 50 states, not fifty states comprise America. In this sentence, America is the whole shebang, so it comes first in the sentence. The whole comprises the parts.
The Meaning of “Compose”
The fly in the ointment as far as the word “comprise” goes is the similar-sounding word “compose,” which means “to make up,” as in “Many ethnic groups compose our nation.”
Notice in this sentence that the parts come before the whole. If you wanted to start the sentence with the words “our nation,” guess which verb you’d have to use instead? Our friend “comprise”: “Our nation comprises many ethnic groups.” So, the parts compose the whole, but the whole comprises the parts.
“Is Comprised Of” and “Is Composed Of”
Now let’s talk about the phrases “is comprised of” and “is composed of.” One of these is allowed, and one is not. The one you can say is “is composed of,” so you could say, “Our nation is composed of many ethnic groups.” On the other hand, most grammar sources I checked (2, 3, 4) agree that “is comprised of” is an incorrect phrase. Just as you can’t say, “The house includes of seven rooms,” you can’t say, “The house is comprised of seven rooms” (5). You have to say, “The house comprises seven rooms.”
How to Use “Comprise”
At first, we said that “comprise” means “contain,” but in her book Woe Is I the respected grammar writer Patricia O'Connor muddies the issue when she lists “to include” as a definition (7). This suggests that there could be more parts to the whole, contradicting the idea that when you use “comprise” you’re talking about all the parts.
If we use this definition, does it mean we could say, “The house comprises at least five rooms”? It would seem to make sense if we substitute the word “include” in this sentence. “The house includes at least five rooms.” Perhaps Fowler’s, another trusted resource, can help us. It states “the whole comprises all the parts.” The word “all” there seems pretty definitive.
On the other hand, the American Heritage Dictionary reveals that “comprise” means “to consist of,” to be composed of,” “to include,” and “to contain” (8). It goes on to clarify matters in its definition of “include”: “Comprise usually implies that all of the components are stated” (9). Notice that it said “usually.” It seems that to use “comprise” you must be talking about all the parts that make up something, but perhaps occasionally you can use it if more parts might be lurking somewhere.
