X X (ĕks). X, the twenty-fourth letter of the English alphabet, has three sounds; a compound nonvocal sound (that of ks ), as in wax ; a compound vocal sound (that of gz ), as in example ; and, at the beginning of a word, a simple vocal sound (that of z ), as in xanthic . See Guide to Pronunciation , §§ 217, 270, 271. The form and value of X are from the Latin X, which is from the Greek Χ, which in some Greek alphabets had the value of ks , though in the one now in common use it represents an aspirated sound of k .

X rays, X-rays X rays, X"-rays` noun plural The Röntgen rays; -- so called by their discoverer because of their enigmatical character.

X-ray tube X"-ray" tube (Physics) A vacuum tube suitable for producing Röntgen rays.

Xanthamide Xanth·am"ide noun [ Xanth ic + amide .] (Chemistry) An amido derivative of xanthic acid obtained as a white crystalline substance, C ₂ H ₅ O.CS.NH ₂ ; -- called also xanthogen amide .

Xanthate Xan"thate noun [ See Xanthic .] (Chemistry) A salt of xanthic; a xanthogenate.

Xanthelasma Xan`the·las"ma noun [ New Latin ; Greek xanqo`s yellow + 'e`lasma a metal plate.] (Medicine) See Xanthoma .

Xanthian Xan"thi·an adjective Of or pertaining to Xanthus , an ancient town on Asia Minor; -- applied especially to certain marbles found near that place, and now in the British Museum.

Xanthic Xan"thic adjective [ Greek xanqo`s yellow: confer French xanthique .] 1. Tending toward a yellow color, or to one of those colors, green being excepted, in which yellow is a constituent, as scarlet, orange, etc. 2. (Chemistry) (a) Possessing, imparting, or producing a yellow color; as, xanthic acid. (b) Of or pertaining to xanthic acid, or its compounds; xanthogenic. (c) Of or pertaining to xanthin. Xanthic acid (Chemistry) , a heavy, astringent, colorless oil, C ₂ H ₅ O.CS.SH, having a pungent odor. It is produced by leading carbon disulphide into a hot alcoholic solution of potassium hydroxide. So called from the yellow color of many of its salts. Called also xanthogenic acid . -- Xanthic colors (Botany) , those colors (of flowers) having some tinge of yellow; -- opposed to cyanic colors . See under Cyanic .

Xanthide Xan"thide noun [ See Xantho- .] (Chemistry) A compound or derivative of xanthogen. [ Archaic]

Xanthidium Xan·thid"i·um noun ; plural Xanthidia . [ New Latin , from Greek xanqo`s yellow.] (Botany) A genus of minute unicellular algæ of the desmids. These algæ have a rounded shape and are armed with glochidiate or branched aculei. Several species occur in ditches, and others are found fossil in flint or hornstone.

Xanthin Xan"thin noun [ Greek xanqo`s yellow.] 1. (Physiol. Chem.) A crystalline nitrogenous body closely related to both uric acid and hypoxanthin, present in muscle tissue, and occasionally found in the urine and in some urinary calculi. It is also present in guano. So called from the yellow color of certain of its salts (nitrates). 2. (Chemistry) A yellow insoluble coloring matter extracted from yellow flowers; specifically, the coloring matter of madder. [ Formerly written also xanthein .] 3. (Chemistry) One of the gaseous or volatile decomposition products of the xanthates, and probably identical with carbon disulphide. [ Obsolete]

Xanthine Xan"thine noun Also Xan"thin [ Greek xanqo`s yellow.] (Physiol. Chem.) A white microcrystalline nitrogenous compound, C ₅ H ₄ O ₂ N ₄ , present in muscle tissue, in the liver, spleen, pancreas, and other organs, and also in urine (in small quantities) and some urinary calculi, and in the juices of certain plants; -- so called because it leaves a yellow residue when evaporated to dryness with nitric acid. Xanthine is closely related to uric acid.

Xanthinine Xan"thi·nine noun [ Greek xanqo`s yellow + qu inine .] (Chemistry) A complex nitrogenous substance related to urea and uric acid, produced as a white powder; -- so called because it forms yellow salts, and because its solution forms a blue fluorescence like quinine.

Xanthium Xan"thi·um noun [ New Latin , from Greek xa`nqion a plant used for dyeing the hair yellow, said to be the Xanthium strumarium , from xanqo`s yellow.] (Botany) A genus of composite plants in which the scales of the involucre are united so as to form a kind of bur; cocklebur; clotbur.

Xantho- Xan"tho- A combining form from Greek xanqo`s yellow; as in xantho cobaltic salts. Used also adjectively in chemistry.

Xanthocarpous Xan`tho·car"pous adjective [ Xantho- + Greek karpo`s fruit.] (Botany) Having yellow fruit.

Xanthochroi Xan·thoch"ro·i noun plural [ New Latin See Xanthochroic .] (Ethnol.) A division of the Caucasian races, comprising the lighter-colored members.

The Xanthochroi , or fair whites, . . . are the prevalent inhabitants of Northern Europe, and the type may be traced into North Africa, and eastward as far as Hindostan.

Tylor.

Xanthochroic Xan`tho·chro"ic adjective [ Xantho- + Greek chro`a color.] (Ethnol.) Having a yellowish or fair complexion; of or pertaining to the Xanthochroi.

Xanthochroid Xan"tho·chroid adjective [ See under Xanthrochroic , -oid .] (Ethnol.) Having a yellowish or fair complexion. -- noun A person having xanthochroid traits.

Xanthochroism Xan·thoch"ro·ism noun Abnormal coloration of feathers in which yellow replaces the normal color, as in certain parrots. It is commonly due to lack of the dark pigment which with yellow forms green.

Xanthodontous Xan`tho·don"tous adjective [ Xantho- + Greek 'odoy`s , 'odo`ntos , tooth.] Having yellow teeth.

Xanthogen Xan"tho·gen noun [ Xantho- + -gen .] (Chemistry) (a) The hypothetical radical supposed to be characteristic of xanthic acid. [ Archaic] (b) Persulphocyanogen. [ R.]

Xanthogenate Xan"tho·gen·ate noun (Chemistry) A salt of xanthic acid.

Xanthogenic Xan`tho·gen"ic adjective [ See Xantho- , and -gen .] (Chemistry) Producing a yellow color or compound; xanthic. See Xanthic acid , under Xanthic .

Xanthoma Xan·tho"ma noun [ New Latin See Xantho- , and -oma .] (Medicine) A skin disease marked by the development or irregular yellowish patches upon the skin, especially upon the eyelids; -- called also xanthelasma .

Xanthomatous Xan·thom"a·tous adjective (Medicine) Of or pertaining to xanthoma.

Xanthomelanous Xan`tho·mel"a·nous adjective [ Prefix xantho- + Greek ..., ..., black.] (Ethnol.) Of or pertaining to the lighter division of the Melanochroi, or those races having an olive or yellow complexion and black hair.

Xanthophane Xan"tho·phane noun [ Xantho- + Greek fai`nein to show.] (Physiol.) The yellow pigment present in the inner segments of the retina in animals. See Chromophane .

Xanthophyll Xan"tho·phyll noun [ Xantho- + Greek fy`llon leaf.] (Botany) A yellow coloring matter found in yellow autumn leaves, and also produced artificially from chlorophyll; -- formerly called also phylloxanthin .

Xanthopous Xan"tho·pous adjective [ Xantho- + Greek poy`s , podo`s , foot.] (Botany) Having a yellow stipe, or stem.

Xanthoproteic Xan`tho·pro·te"ic adjective (Physiol. Chem.) Pertaining to, or derived from, xanthoprotein; showing the characters of xanthoprotein; as, xanthoproteic acid; the xanthoproteic reaction for albumin.

Xanthoprotein Xan`tho·pro"te·in noun [ Xantho- + protein .] (Physiol. Chem.) A yellow acid substance formed by the action of hot nitric acid on albuminous or proteid matter. It is changed to a deep orange-yellow color by the addition of ammonia.

Xanthopuccine Xan`tho·puc"cine noun [ Xantho- + pucc oon + -ine .] (Chemistry) One of three alkaloids found in the root of the yellow puccoon ( Hydrastis Canadensis ). It is a yellow crystalline substance, and resembles berberine.

Xanthorhœa Xan`tho·rhœ"a noun [ New Latin , from Greek xanqo`s yellow + "rei^n to flow.] (Botany) A genus of endogenous plants, native to Australia, having a thick, sometimes arborescent, stem, and long grasslike leaves. See Grass tree .

Xanthorhamnin Xan`tho·rham"nin noun [ Xantho- + New Latin Rhamnus , the generic name of the plant bearing Persian berries.] (Chemistry) A glucoside extracted from Persian berries as a yellow crystalline powder, used as a dyestuff.

Xanthorhiza Xan`tho·rhi"za noun [ New Latin , from Greek xanqo`s yellow + "ri`za root.] (Botany) A genus of shrubby ranunculaceous plants of North America, including only the species Xanthorhiza apiifolia , which has roots of a deep yellow color; yellowroot. The bark is intensely bitter, and is sometimes used as a tonic.

Xanthose Xan"those noun (Chemistry) An orange-yellow substance found in pigment spots of certain crabs.

Xanthosis Xan·tho"sis noun [ New Latin , from Greek xanqo`s yellow.] (Medicine) The yellow discoloration often observed in cancerous tumors.

Xanthospermous Xan`tho·sper"mous adjective [ Xantho- + Greek spe`rma sperm.] (Botany) Having yellow seeds.

Xanthous Xan"thous adjective [ Greek xanqo`s yellow.] Yellow; specifically (Ethnol.) , of or pertaining to those races of man which have yellowish, red, auburn, or brown hair.

Xanthoxylene Xan·thox"y·lene noun [ See Xanthoxylum .] (Chemistry) A liquid hydrocarbon of the terpene series extracted from the seeds of a Japanese prickly ash ( Xanthoxylum pipertium ) as an aromatic oil.

Xanthoxylum Xan·thox"y·lum noun [ New Latin , from Greek xanqo`s yellow + xy`lon wood.] (Botany) A genus of prickly shrubs or small trees, the bark and rots of which are of a deep yellow color; prickly ash. » The commonest species in the Northern United States is Xanthoxylum Americanum . See Prickly ash , under Prickly .

Xebec Xe"bec (zē"bĕk) noun [ Spanish jabegue , formerly spelt xabeque , or Portuguese xabeco ; both from Turk. sumbeki a kind of Asiatic ship; confer Persian sumbuk , Arabic sumbūk a small ship.] (Nautical) A small three-masted vessel, with projecting bow stern and convex decks, used in the Mediterranean for transporting merchandise, etc. It carries large square sails, or both. Xebecs were formerly armed and used by corsairs.

Xeme Xeme (zēm) noun (Zoology) An Arctic fork-tailed gull ( Xema Sabinii ).

Xenelasia Xen`e·la"si·a noun [ New Latin , from Greek xenhlasi`a expulsion of strangers.] (Gr. Antiq.) A Spartan institution which prohibited strangers from residing in Sparta without permission, its object probably being to preserve the national simplicity of manners.

Xenium Xe"ni·um noun ; plural Xenia . [ Latin , from Greek xe`nion gift to a guest, from xe`nos guest.] (Class. Antiq.) A present given to a guest or stranger, or to a foreign ambassador.

Xenodochium Xen`o·do·chi"um noun [ Late Latin , from Latin xenodochium a building for the reception of strangers, Greek ... .] (a) (Class. Antiq.) A house for the reception of strangers. (b) In the Middle Ages, a room in a monastery for the reception and entertainment of strangers and pilgrims, and for the relief of paupers. [ Called also Xenodocheion .]

Xenodochy Xe·nod"o·chy noun [ Greek ....] Reception of strangers; hospitality. [ R.]

Xenogamy Xe·nog"a·my noun [ Greek xe`nos strange, foreign + ... marriage.] (Botany) Cross fertilization.

Xenogenesis Xen`o·gen"e·sis noun [ Greek xe`nos a stranger + English genesis .] (Biol.) (a) Same as Heterogenesis . (b) The fancied production of an organism of one kind by an organism of another. Huxley.