Comprise, compose and consist have come to my attention quite forcibly this week, as I keep coming across examples of them being used incorrectly. Or, rather, comprise being used incorrectly. “Comprise of” and, in the past tense, “comprised of” seem to be getting more and more common, and the three words do have a similar meaning, in that they are all about larger things being made up of smaller things. But the way they are used, and the constructions that are built around them, are different and do need care. There is also a subtle shift in emphasis from the parts to the whole, which I’ll describe as I go through them.
The problem creeps in when they are not adequately differentiated in the writer’s mind, in which case the constructions leak across from one to another, causing (gasp!) incorrect sentence structures. And yes, there is a school of thought that says “if you can understand it, it doesn’t matter if it’s a bit incorrect or clumsy”, but I don’t think there’s any need to be incorrect and clumsy if you don’t have to be. There, I’ve said it. Anyway, here goes!
To comprise is to consist of (yes, I know), be made up of: “the country comprises four regions”. But not (please!) “the country comprises of four regions”. If you are desperate to use “of”, then you can turn the verb around and make the country the subject, so: “the country is comprised of four regions”. But I’ll repeat again, it’s not comprises of, and really I don’t much like is comprised of much, either, when it comes down to it, and if you write that in something I’m editing, I’m likely to suggest changing it!
The emphasis here is very much on the smaller constituent parts. We’re talking about what the larger thing is made up of, and they are the important things, rather than the whole.
Note that the large thing comprises the small things. The small things don’t really comprise the big one, or at least we don’t write it that way round.
To consist of means to be made up of – “the country consists of four regions”. You can use that “of” as much as you like with consist! The emphasis here is on the parts that make up the whole, but also on the fact that they do make up a whole, so there’s an equal balance of importance.
And a little bonus: to consist in means to have as an essential feature – “Bob and Tom look very similar: their difference consists in the way they talk”.
If you can replace “consists” with “lies”, then use in. If you can replace “consists” with “is made up” then use of.
To be composed of, again, means to be made up of, although the emphasis shifts here subtly to the whole: the parts compose the whole, and the whole is what is important. “The work is composed of four movements”.