Time class question about "comprise":

How can we use the word "comprise"? Is the preposition "of" necessary?

Strict grammarians say that comprise should be used as an active-voice verb without the addition of the preposition of "of."

Japan comprises 47 prefectures.

The use of comprise is still considered nonstandard by the strictest of grammarians. But in daily conversation I think you can safely say:

Japan is comprised of 47 prefectures.

To be on the safe side here in formal situations (or just to avoid confusion when using "comprise"), you might want to use the phrase "consistof."

Japan consists of 47 prefectures.