macro- In general, no hyphen after this prefix: macrobiotics, macroclimate, macrocytosis, macroeconomics, macromolecule, macroscopic. See Words Formed with Prefixes under General Style Preferences.

macroeconomics, microeconomics No hyphen.

make up (v.), makeup (n. and adj.)

may, might The word may expresses what is possible, is factual, or could be factual: I may have turned off the computer, but I can’t recall doing it. The word might suggests something that is uncertain, hypothetical, or contrary to fact: I might have won the contest if I had entered.

medium, media In scientific contexts and in reference to mass communications, the plural of medium is media: Photolithography was her chosen medium. The idea that the news media are shrinking is mistaken.

mega- In general, no hyphen after this prefix, except to separate two a’s: megabyte, megahertz, megavitamin, megaton. See Words Formed with Prefixes under General Style Preferences.

memorandum (singular), memoranda (plural): Although both the plural forms memoranda and memorandums are correct, memoranda is more common. (Chicago Manual style; this is an exception to AP style, which uses memorandums as the plural.) The short versions are memo, memos.

menswear Not men’s wear.

meta- In general, no hyphen after this prefix, except to separate two a’s: metadata, metaethical, metafiction, metalinguistics, metaphysical; meta-analysis. See Words Formed with Prefixes under General Style Preferences.

micro- In general, no hyphen after this prefix: microbiology, microclimate, microchemistry, microeconomics, micromanage, microorganism. See Words Formed with Prefixes under General Style Preferences.

mid- In general, no hyphen after this prefix, unless it is followed by a proper name: midterm, midsemester, midair; mid-Atlantic. See Words Formed with Prefixes under General Style Preferences.

millennium Double l, double n.

mini- See Words Formed with Prefixes under General Style Preferences.

minuscule Not miniscule (a spelling error).

more than, over See over, more than.

Mount Spell out in all cases: Mount Vernon, Mount Rushmore.

mpg Acceptable in all references for miles per gallon.

mph Acceptable in all references for miles per hour.

mock-up (n.)

modifiers Keep modifiers close to the words they modify: Students are required to purchase only one textbook for that course, not Students are only required to purchase one textbook for that course.

multi- No hyphen is used after this prefix, except to separate two i’s: multicultural, multipurpose; multi-institutional. See Words Formed with Prefixes under General Style Preferences.

myriad (adj.) It means “constituting an extremely large, indefinite number” (the myriad fish in the ocean) or “composed of numerous diverse elements or facets” (the myriad responsibilities of parents). Do not follow with the word of.

Updated June 27, 2014