DECIDUOUS

(Lat. decido, I fall off.) In Zoology, a term applied to parts which have but a temporary existence, and are shed during the life-time of the animal, as certain kinds of hair, horns, and teetii. Deci'duo us is applied, in Botany, to plants whose leaves fall off" in the autumn, in contradistinction to evergreens. DECIMAL ARITHMETIC, is the common system of arithmetic, in which the scale of numbers proceeds by tens. See Arithmetic. DECIMAL FRACTIONS, are fractions which have for their denominator 10. 100, 1000, ., or in general some power of 10. The use of decimal fractions is merely an extension of the ordinary scale of arithmetical notation. Setting out from the unit's place, the first figure to the left (in the expre ion of any whole number) denotes so many tens, the second to the left so many hundreds, the third so many you sands, and so on; so that in the number 765, for example, each unit of the 6 is the tenth part of each unit of the 7, and each unit of the 5 a tenth of each unit of the 6. In like manner, in the expre ion of a decimal fraction, setting out from the unit's place, the first figure to the right expre es so many tenth parts, the second to the right so many hundredth parts, the third so many thousandths, and so on; so that each figure, as before, expre es parts, which are each ten times smaller than those expre ed by the figure immediately preceding. By expre ing fractions in this manner, the operations of addition, subtraction, multiplication, and division are exactly the same as in integer numbers. 317 DECLINATION OF A [s. 330]