‘Compose’ and ‘comprise’ are two verbs that are easy to mix up if the writer isn’t aware of their differences.
‘Compose’ means ‘to form by putting together,’ while ‘comprise’ means ‘to include, contain, or consist of.’ In both cases, we are dealing with parts and a whole. Hint: when using ‘comprise,’ the whole always comes before the parts in the sentence.
The United States comprises 50 states.
Fifty states compose the United States.
NOTE: Most grammarians insist that ‘is comprised of’ is an incorrect phrase.
Although you will find some sources that will allow its usage, the Handbook of Technical Writing, the Chicago Manual of Style, and the Associated Press Style Guide (among others) insist that the use of ‘comprised of’ is incorrect.
The following was taken directly from the Chicago Manual of Style:
comprise; compose. 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 or consisting of.
Incorrect usage is stealthily slithering its way into the English language. (Don’t get me started!)
So please–learn the correct usage and stay strong!