M

material, materiel--The more common of these words, material (muh-TIR-i-uhl)
means "matter," "substance," "constituent element." Materiel (muh-TEER-i-el)
is usually limited to equipment or supplies.

mean, median, average--An average is a typical
value or quantity in some set of values or quantities. The arithmetic mean of a
set of values is one kind of average: the number obtained by dividing
the sum of the set of values by the number of values in the set. Average
often refers to arithmetic mean. The median of a distribution is
the middle value, above and below which lie an equal number of values. A median
is another kind of average.

medium, media--These words refer to an agency, means, method, or
instrument by which information and advertising may be made public. Such
agencies and means include newspapers, magazines, radio and television
broadcasting, and films. The singular is medium and the plural is mediums
or media. Medias is an incorrect plural.

Television is an important medium for national
advertisers.

moot--This word has two ostensibly conflicting definitions: "arguable"
and "no longer requiring argument." To avoid ambiguity, use the word only when
referring to something that could have been open to debate but because of
circumstances is no longer an issue.

Our experiment would have been a great success, but the point
is moot; our funding has been cut.

mutual, common--Mutual means "reciprocally
exchanged between two persons or things." Common means "shared by all."