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Compose vs. Comprise
Composed and comprised basically mean the same thing (“to be made of,” “to consist of”). They’re often used interchangeably, although grammar sticklers often insist that they shouldn’t be. “Never use to be comprised of,” instructs the CDC Style Guide [PDF – 1.4 MB] (which was last updated in 2003). In 2017, no less an authority than Writing Tip Wednesday [PDF – 433 KB] exclaimed, “Is comprised of is never correct!” The Chicago Manual of Style, CDC’s main style guide of the moment, agrees:
“comprise; compose. Use with care. To comprise is “to consist 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 is comprised of, though increasingly common, remains nonstandard. Instead, try is composed of or consists of.”
However, two important sources have a less strict stance on comprised of. Grammarly suspects that it’s slowly becoming standard usage. Merriam-Webster (MW) says, “although it has been in use since the late 18th century, [it] is still attacked as wrong. Why it has been singled out is not clear.” MW, however, still advises avoiding comprised of if you don’t want to be harassed by the grammar police.
Both of the following examples are grammatically correct:
The United States comprises 50 states.
The United States is composed of 50 states.
But we here at Writing Tip Wednesday are going to go out on a limb: Neither of them is the best choice. If writing like you talk is a goal of clear communication [PDF – 4.6 MB] (and it is), the above sentences do not fit the bill. We suggest avoiding the issue altogether and reaching for a simpler word. “The United States has 50 states” does the job perfectly well.