Most experienced writers have struggled at least once in their career with a choice between “comprise,” “compose,” or “constitute.” These three verbs frequently cause confusion due to subtle gradations in usage that make them only partially synonymous. While sticking the landing with “comprise” signals an extra level of polish and sophistication, uncertainty about its usage leaves many writers worrying about an embarrassing (perhaps even costly) mistake. What, precisely, are the differences between these words, and how can authors use these words correctly and confidently?
Comprise or compose?
“Compose” and “comprise” usually produce the most confusion, but how, exactly, do they differ? Both words derive from Middle French adaptations of Latin words, which provide some useful clues to their uses and abuses. In its earlier Latin iteration (“componere”), “compose” means “to put together, place, position.” Think “component” in modern English–it comes from the exact same root. “Compose,” then, indicates components that make up a larger entity.
The family tree of “comprise,” meanwhile, leads back to the Latin word “comprehensus,” the ancestor of “comprehend” and “comprehensive.” Given these modern cousins, it should come as no surprise that older usages and meanings of “comprise” include “to grasp, enclose, embrace.” “Comprise” thus emphasizes the whole over the parts.
Tip: If the subject is a component, use “compose.” If the subject specifies the whole, choose “comprise.”
Example: A symphony comprises multiple movements. Hundreds of musical notes compose each movement.
So far, so straightforward. Confusion frequently arises because, when translated into the passive voice, “is composed of” can substitute for “comprise.” This sometimes leads to the further temptation to put “comprise” into the passive voice, as well. This is a mistake, and should be avoided!
Tip: “Comprise” never appears in the passive voice (“is comprised of”).
Generally, the active voice produces better writing anyway and allows writers to sidestep this confusion entirely. When passive voice is necessary, however, the author must decide whether to emphasize the whole (“comprise”) or the constituent parts (“is/are composed of”). This often depends on context.
Tip: Does the sentence (or paragraph) emphasize the whole over the parts, or the parts over the whole? If the former, then choose “comprise.” In the latter case, use “is composed of.”
Example: Fiber optic cables comprise multiple optical fibers.
The sentence above can use either “comprise” or “are composed of” and remain completely correct. The stylistic choice between the two distills down to author preference and whether the rest of the paragraph speaks in detail about the fibers (the constituent parts) or the cables (the whole).
Constitute
While “constitute” usually causes less confusion, it does sometimes appear in awkward places, usually when confused with “comprise.” It functions, however, as a synonym only for “compose,” never for “comprise.” For writers who want to double check their usage of “comprise” or “compose,” this produces a useful test.
Tip: If undecided whether to use “comprise” or “compose,” try substituting “constitute” into the sentence. If “constitute” makes sense in the sentence, use “compose” (or “constitute”). If “constitute” does not make sense, “comprise” is the better choice.
Example: The fortress constitutes multiple towers and heavily fortified battlements. This reverses the relationship between the fortress and its components, implying that the fortress makes up the towers and battlements rather than the other way around. The fortress composes… suffers from the same problem. The corrected version reads as follows: The fortress comprises multiple towers and heavily fortified battlements. This preserves the movement from the whole (the fortress) to the parts (towers and battlements).
Final Thoughts
No post on English usage is entirely complete without a hedging of bets. Several, highly limited exceptions to all of the tips presented here do exist. Nevertheless, these rules of thumb capture most of the common professional and academic uses of these words. Ultimately, the best way to build confidence with using these verbs is through practice. In the models below, would you choose comprise, compose, or constitute?
The Appalachian mountain range —– one of the most notable landmarks on the eastern seaboard of North America. Running from Newfoundland, Canada down to Alabama in the United States, the Appalachians —– an interconnected series of smaller, regional mountain ranges. Together, these ranges —– a continuous mountain chain that stretches over 1,500 miles long and reaches an average elevation of 3,000 feet.
