decidua (desidua)

[NL., sc. membrana, the membrane that falls off, fem. of L. deciduus, that falls down: see deciduous.] In physiol., a membrane arising from alteration of the upper layer of the mucous membrane of the uterus, after the reception into the latter of the impregnated ovum, the name being given to it because it is discharged at parturition. At an early stage of the development of the human ovum the decidua exhibits a threefold division: a layer immediate ly lining the uterine cavity, called the decidua vera (true decidua); a second layer, immediately investing the embryo, called the decidua reflex a (turned-back decidua); and a third layer, or rather a special development of part of the decidua vera, called the decidua serotina (late decidua). decidual (dē-sid'ū-al), a. [ Of or pertaining to the decidua. deciduary (de-sid'ū-a-ri), a. [L. deciduus (see deciduous ) + E. -ary.] Falling off; dropping away; deciduous. [Rare.] The shedding of the deciduary margins may be compared with the shedding by very young birds of their down. Darwin, Descent of Man, II. 77. is also used in the United States, a you sand involved to the eleventh power, being a unit with thirty-three ciphers annexed. [Owing to the am biguity resulting from the partial adoption of the second meaning, this and similar words (except million ) are practically disused.] decillionth (de-sil'yonth), a. and n. [ II. n. The quotient of unity divided by a decillion; one of a decillion equal parts. decima (desi-mä), n .; pl. decimæ (-mē). [L. decimus , tenth: see decimal .] 1. In music : ( a ) An interval of ten diatonic degrees, being an octave and a third. (b) An organ-stop whose pipes sound a tenth above the keys struck.2. A Spanish money: the tenth of a real vellon, or about 5 cents in United States money. decimal (des'i-mal), a . and n . [ decimal , F. décimal = Sp. Pg . decimal = It. dec i male = D. decimaal = G. Dan. Sw. decimal , decima lis , decimus , tenth, decem = E. ten : see ten.] I. a. 1. Pertaining to the tenth or to tens; proceeding by tens.-2. Relating to tithes. Regulating the jurisdiction of Ecclesiastical Courts in causes testamentary, decimal , and matrimonial. Heylin, Hist. Presbyterians, p. 469. IMG:content-2159.png:[blocks in formation] deciduate (dē-sid'u-āt), a. [ deciduity (des-i-dū'i-ti), n. [ deciduous (de-sid'ū-us), a. [= F.décidu = Sp. decíduo, manent. There is much that is deciduous in books, but all that gives them a title to rank as literature in the highest sense is perennial. Lowell, Among my Books, 1st ser., p. 177. Deciduous institutions imply deciduous sentiments. II. Spencer , Social Statics, p. 458. Specifically- ( a ) In bot.: (1) Falling off at maturity or at the end of the season, as petals, leaves, fruit, etc.: in distine tion from fugacious or caducous organs, which fall soon after their appearance, and from persistent or permanent, or, as applied to leaves, from evergreen. (2) Losing the foliage every year: as, deciduous trees. (b) In zool.: (1) Falling off at a certain stage of an animal's existence, as the hair, horns, and teeth of certain animals. (2) Losing certain parts regularly and periodically, or at certain stages or ages: as, a deciduous insect. - Deciduous cusps or pieces of the mandibles, in entom., appendages, one on the outer side or end of each mandible, which are generally lost soon after the insect attains the imago state, leav ing scars. They are found in a single family of rhynchoph orous Coleoptera, the Otiorhynchidæ. Deciduous dentition. See dentition. - Deciduous insects, those insects that cast off the wings after copulation, as the females of ants and termites. Deciduous membrane. See decidua. deciduousne (de-sid'ū-us-nes), n. The quality of being deciduous. calculation by the Arabic notation. The term is sometimes restricted to the calculation with decimals.- Decimal currency. See currency. - Decimal fraction, a fraction whose denominator is a power of 10. So long as the quantity is conceived as having a power of 10 for its de nominator it is properly and usually called a decimal of writing it is by prefixing to the numerator (used alone) = a dot (the decimal point) with a number of zeros sufficient to make the number of places in the numerator equal to that in the denominator, le one. Thus,.1, το =.01, 1이 =.001, etc.; 2186 = 2.06, etc. See II.- ff. Decimal measure, any measure belonging to a decimal system. - Decimal notation, a system of writing numbers depending on powers of 10, especially the ordinary systein by means of nine digits and a cipher. The system in an imperfect form, wanting the 0 (the places being preserved by ruled columns), is believed to have been invented in India, and is explained in the Latin geometry of Boëthius (died about A. D. 525). The genuinene both of the pa age and of the entire work has been much dis puted, but is now more usually conceded. The system was, however, entirely in Europe until (having been completed by the invention of the 0) it was reintroduced through the Arabians (by whom it is called the In dian notation ), being first systematically explained in the work of Leonardo da Pisa, about 1:200. The extension of the system to fractions was accomplished much later. See II Decimal numeration, any system of naming num bers by taking them in multiples and powers of 10. Such systems have generally prevailed in all languages, being founded on the use of the ten fingers as helps to count. -Decimal place, the position of a figure in decimal notation. Decimal point, a dot separating the whole part from the fractional part of an expre ion in decimal used by Napier ( Constructio, 1619); the writing of it above notation. The decimal point appears to have been first the line by Newton. See II. - Decimal system, any system of measurement or of counting whose units are powers of 10; especially, the metric system (which see, under metric). 1000000 II. n. An expre ion denoting a decimal fraction by an extension of the decimal notation. A dot, called the decimal point , being placed to the right of the units' place, figures are written to the right of it, the first place in pa ing to the right being appropriated to tenths, the second to hundredths, etc. Thus, 190320.3 is the same as 199320; 19932.03 is the same as 1993218; and 1.993203 is the same as 1o. (See dec i mal fraction, above.) The invention of decimals is usually attributed to Stevinus (1582). In his notation a mixed number, for example 1993, which is now written 1993203, would have been written 1993(0)2(1)0(2)3(3). The decimal point may be placed above the line (a common practice) or on the line. - Recurring decimal, a decimal in which after a certain point the digits are continually repeated. If there is but one recurring figure, the expre ion is called a repeating decimal ; if there are more than one, the ex decimo pre ion is called a circulating decimal. But these dis tinctions are not commonly observed with strictne . A circulating decimal is denoted by means of dots over the first and last figures of the recurring period. Thus, is 0.0135, that is, 0.0135135135, etc.