library classification system that organizes information into 10 broad areas subdivided numerically into progressively smaller topics, by 1885, named for Melvil Dewey (1851-1931) who proposed it 1876 while acting librarian of Amherst College. He also crusaded for simplified spelling and the metric system.

early 15c., numeracioun, "method or process of numbering or calculating," from Latin numerationem (nominative numeratio) "a counting out, paying, payment," noun of action from past-participle stem of numerare "to count, number," from numerus "number" (see number (n.)). Meaning "act or process of counting the number of" is from mid-15c.

c. 1600, "pertaining to a tenth or ten," from Medieval Latin decimalis "of tithes or tenths," from Latin decimus "tenth," from decem "ten" (from PIE root *dekm- "ten"). Applied to Arabic notation before modern use in reference to decimal fractions (fraction whose denominator is a power of 10) emerged 1610s. As a noun from 1640s, "a decimal fraction." **Decimal point** is by 1711; the use of the point seems to be due to Scottish mathematician John Napier, "Marvellous Merchiston," c. 1619.

Meaning "set of correlated principles, facts, ideas, etc." first recorded 1630s. Meaning "animal body as an organized whole, sum of the vital processes in an organism" is recorded from 1680s; hence figurative phrase to get (something) out of one's system (1900). Computer sense of "group of related programs" is recorded from 1963. All systems go (1962) is from U.S. space program. The system "prevailing social order" is from 1806.

also metre, "fundamental unit of length of the metric system," originally intended to be one ten-millionth of the length of a quadrant of the meridian, 1797, from French mètre (18c.), from Greek metron "measure," from PIE root *me- (2) "to measure." Developed by French Academy of Sciences for system of weights and measures based on a decimal system originated 1670 by French clergyman Gabriel Mouton.

1680s, from French billion (originally byllion in Chuquet's unpublished "Le Triparty en la Science des Nombres," 1484; copied by De la Roche, 1520); see bi- "two" + million. A million million in Britain and Germany (numeration by groups of sixes), which was the original sense; subsequently altered in French to "a thousand million" (numeration by groups of threes) and picked up in that form in U.S., "due in part to French influence after the Revolutionary War" [David E. Smith, "History of Mathematics," 1925]. France reverted to the original meaning in 1948. British usage is truer to the etymology, but U.S. sense is said to be increasingly common there in technical writing.

In Italian arithmetics from the last quarter of the fifteenth century the words bilione or duilione, trilione, quadrilione or quattrilione, quintilione, cinquilione, or quinquilione, sestione or sestilione, settilione, ottilione, noeilione and decilione occur as common abbreviations of due volte millioni, tre volte millione, etc. In other countries these words came into use much later, although one French writer, Nicolas Chuquet, mentions them as early as 1484, in a book not printed until 1881. The Italians had, besides, another system of numeration, proceeding by powers of a thousand. The French, who like other northern peoples, took most if not all their knowledge of modern or Arabic arithmetic from the Italians, early confounded the two systems of Italian numeration, counting in powers of a thousand, but adopting the names which properly belong to powers of a million. [Century Dictionary]

For a time in Britain gillion (1961), based on giga-, was tried as "a thousand million" to avoid ambiguity. Compare milliard.