c. 1400, decessioun, "departure, separation;" c. 1600, "decrease from a standard, diminution," from Latin decessionem(nominative decessio) "a going away, departure," noun of action from past-participle stem of decedere "to go down, depart," from de "away" (see de-) + cedere "to go" (from PIE root *ked- "to go, yield").
in the metric system, word-forming element denoting one-tenth of the standard unit of measure, 1801, from French deci-, taken arbitrarily from Latin decimus "tenth," from decem "ten" (from PIE root *dekm- "ten").
Progress in science and industry is constantly demanding new terms and one of the latest of these is the word "decibel," coined by telephone engineers to describe the efficiency of telephone circuits. It is a substitute for the phrase "transmission unit." The actual unit decided upon was first called "bel," after the inventor of the telephone. The bel, however, is larger than is needed in practice, and, therefore, a unit one-tenth as large was adopted by engineers and named the decibel. [Popular Mechanics, May 1929]
late 14c., "to settle a dispute, determine a controversy," from Old French decider, from Latin decidere "to decide, determine," literally "to cut off," from de "off" (see de-) + caedere "to cut" (from PIE root *kae-id- "to strike"). For Latin vowel change, see acquisition. Sense is of resolving difficulties "at a stroke." Meaning "to make up one's mind" is attested from 1830. Related: Decided; deciding.
1680s, with reference to leaves, petals, teeth, etc., "falling off at a certain stage of existence," from Latin deciduus "that which falls down," from decidere "to fall off, fall down," from de "down" (see de-) + combining form of cadere "to fall," from PIE root *kad- "to fall." Of trees and bushes, "losing foliage every year" (opposed to evergreen), from 1778. The Latin adjective was used of shooting stars and testicles, but it seems not to have been used of trees or leaves (the phenomenon in Italy seems to be restricted to the mountain regions). Related: Deciduousness.
1670s in astrology, of planets, "one-tenth part of the zodiac distant from one another;" 1882 in statistics; from French décile or Medieval Latin *decilis, from Latin decem "ten" (from PIE root *dekm- "ten") on the model of quintilis, sextilis.
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.
