M

Noun
concentration measured by the number of moles of solute per liter of solvent

Noun
the 13th letter of the Roman alphabet

Noun
the basic unit of length adopted under the Systeme International d''Unites (approximately 1.094 yards)

Noun
the cardinal number that is the product of 10 and 100

Adjective S.
denoting a quantity consisting of 1,000 items or units

As a numeral, M stands for one thousand, both in English and Latin.

n.
A quadrat, the face or top of which is a perfect square; also, the size of such a square in any given size of type, used as the unit of measurement for that type: 500 m's of pica would be a piece of matter whose length and breadth in pica m's multiplied together produce that number.

n.
A brand or stigma, having the shape of an M, formerly impressed on one convicted of manslaughter and admitted to the benefit of clergy.