a form of instability which is a property of the atomic nuclei of certain isotopes, which causes a spontaneous change in the structure of the nucleus, accompanied by emission of energetic radiation. The radiation emitted is usually sufficient to cause ionization in matter through which it passes, and is therefore called ionizing radiation. The radiation emitted by most radioactive substances is one of three types: alpha rays, beta rays, or gamma rays. Some chemical elements have no stable isotopes, and these are referred to as radioactive elements, and the element itself is said to possess radioactivity.

A substance or device that has its conductivity altered in some way by electric waves, as a coherer.

To make a radiograph of.

Art or process of making radiographs, radiograms, or autoradiograms.

Order of rhizopods, usually having a siliceous skeleton, or shell, and sometimes radiating spicules. The pseudopodia project from the body like rays. It includes the polycystines. See Polycystina.

Of or pertaining to the Radiolaria. One of the Radiolaria.

The barbs of the radii of a feather; barbules.

A hippurite.

A forestaff.

The use of the radiometer, or the measurement of radiation.

A very sensitive modification or application of the thermopile, used for indicating minute changes of radiant heat, or temperature.

A radiotelegraphic station serving solely for determining the position of ships. The radius of operation of such stations was restricted by the International Radiotelegraphic Convention (1912) to 30 nautical miles.

An apparatus for the production of sound by the action of luminous or thermal rays. It is essentially the same as the photophone.

The art or practice of using the radiophone.

See Projector, above.

Direct observation of objects opaque to light by means of some other form of radiant energy, as x-rays.

A message transmitted by radiotelegraph.

A wireless telegraph.

Of or pertaining to radiotelegraphy; employing, or used or employed in, radiotelegraphy.

Telegraphy using the radiant energy of radio waves; wireless telegraphy; -- the term adopted for use by the Radiotelegraphic Convention of 1912.

A wireless telephone, in which the signal is conveyed by radio waves.

Treatment of disease by means of x-rays or radioactivity. Radiotherapy of cancer is based on the fact that cancer cells are more sensitive to radiation than most other cells in the body.

an earlier name for the thorium isotope thorium-228, given by its discoverer Otto Hahn. It is a radioactive substance formed as one of series of products in the chain of radioactive decay of thorium. Its immediate predecessor in the chain is Actinium-228, and it decays by alpha emission to radium-224 with a half-life of 1.91 years. The name radiothorium was given prior to the full understanding of the nature of isotopes of elements.

Consisting of rays, as light.

The pungent fleshy root of a well-known cruciferous plant (Raphanus sativus); also, the whole plant.

An intensely radioactive metallic element found (combined) in minute quantities in pitchblende, and various other uranium minerals. Symbol, Ra; atomic weight, 226.4. Radium was discovered by M. and Mme. Curie, of Paris, who in 1902 separated compounds of it by a tedious process from pitchblende. Its compounds color flames carmine and give a characteristic spectrum. It is divalent, resembling barium chemically. The main isotope of radium found in pitchblende, radium-226, has a half-life of 1620 years, decaying first by alpha emission to radon.

A right line drawn or extending from the center of a circle to the periphery; the semidiameter of a circle or sphere.

A straight line (or the length of such line) connecting any point, as of a curve, with a fixed point, or pole, round which the straight line turns, and to which it serves to refer the successive points of a curve, in a system of polar coordinates. See Coordinate, n.

A primitive word, from which spring other words; a radical; a root; an etymon.

An intensely radioactive gaseous element produced by the radioactive decay of radium-226, which is the main isotope of radium found in pitchblende. Chemically it is an inert noble gas. Its atomic symbol is Rn. It has an atomic number of 86. The radon isotope produced by decay of radium has an atomic weight of 222.017, and this isotope decays by alpha emission with a half-life of 3.82 days. Numerous other isotopes have been observed, all radioactive and all having half-lives shorter than that of radon-222. Radon was discovered by M. and Mme. Curie, of Paris, in their studies of the radioactive substances in pitchblende. Radon was originally called radium emanation or exradio.

The chitinous ribbon bearing the teeth of mollusks; -- called also lingual ribbon, and tongue. See Odontophore.

Rasplike; as, raduliform teeth.

A promiscuous heap; a jumble; a large quantity; lumber; refuse.

Raphaelesque.

A fibrous material used for tying plants, said to come from the leaves of a palm tree of the genus Raphia.

A colorless crystalline slightly sweet substance obtained from the molasses of the sugar beet.

Resembling, or having the character of, raff, or a raff; worthless; low.

To dispose of by means of a raffle; -- often followed by off; as, to raffle off a horse.

One who raffles.

A genus of stemless, leafless plants, living parasitically upon the roots and stems of grapevines in Malaysia. The flowers have a carrionlike odor, and are very large, in one species (Rafflesia Arnoldi) having a diameter of two or three feet.

To transport on a raft, or in the form of a raft; to make into a raft; as, to raft timber.

imp. of Reave.

To make into rafters, as timber.

The business of making or managing rafts.

A man engaged in rafting.

Damp; musty.

To play or compose (a piece, melody, etc.) in syncopated time.

An idle, ragged person.

A paltry or disreputable fellow; a mean wretch.

To enrage.

Full of rage; expressing rage.

Wantonness.

Rent or worn into tatters, or till the texture is broken; as, a ragged coat; a ragged sail.

Notched in regular diagonal breaks; -- said of a line, or a bearing having such an edge.

Ragged; rough.

A celebrated Sanskrit poem having for its subject the Raghu dynasty.

a. n. from Rage, v. i.

Raging; furious; rageful.

A loose overcoat with large sleeves; -- named after Lord Raglan, an English general who was an aide-de-camp to Wellington at Waterlooo.

A sleeve joined to the body of a garment by a long slanting seam starting at the neck and continuing around the armhole. Contrasted to a set-in sleeve.

The so-called /Twilight of the Gods/ (called in German G/tterd/mmerung), the final destruction of the world in the great conflict between the Aesir (gods) on the one hand, and on the other, the giants and the powers of Hel under the leadership of Loki (who is escaped from bondage).

A dish made of pieces of meat, stewed, and highly seasoned; as, a ragout of mutton.

One who gets a living by picking up rags and refuse things in the streets.

a rhythm with a regular accompaniment in two-four time and a melody characterized by syncopation, first recognized in many negro melodies; also a style of American music in this rhythm.

A common American composite weed (Ambrosia artemisiaefolia) with finely divided leaves; hogweed.

A kind of rubblework. In the United States, any rubblework of thin and small stones.

A name given to several species of the composite genus Senecio.

A genus of rays which includes the skates. See Skate.

The order of elasmobranch fishes which includes the sawfishes, skates, and rays; -- called also Rajae, and Rajii.

To make a raid upon or into; as, two regiments raided the border counties.

One who engages in a raid.

Designating, or pertaining to, a form of cooperative bank founded among the German agrarian population by Friedrich Wilhelm Raiffeisen (1818-88); as, Raiffeisen banks, the Raiffeisen system, etc. The banks are unlimited-liability institutions making small loans at a low rate of interest, for a designated purpose, to worthy members only.

To rail at.

One who rails; one who scoffs, insults, censures, or reproaches with opprobrious language.

A barrier made of a rail or of rails, together with vertical supports. The typical railing in the interior of structures or on porches has a horizontal rail near waist height, and multiple vertical supports. Its function is usually to provide a safety barrier at the edge of a verticle drop to prevent falls.

With scoffing or insulting language.

Pleasantry or slight satire; banter; jesting language; satirical merriment.

A banterer; a jester; a mocker.

To carry or send by railroad; usually fig., to send or put through at high speed or in great haste; to hurry or rush unduly; as, to railroad a bill through Condress.

The construction of a railroad; the business of managing or operating a railroad.

A road or way consisting of one or more parallel series of iron or steel rails, patterned and adjusted to be tracks for the wheels of vehicles, and suitably supported on a bed or substructure.

Clothing in general; vesture; garments; -- usually singular in form, with a collective sense.

To pour or shower down from above, like rain from the clouds.

So tight as to exclude rain; as, a rain-tight roof.

A bow or arch exhibiting, in concentric bands, the several colors of the spectrum, and formed in the part of the hemisphere opposite to the sun by the refraction and reflection of the sun's rays in drops of falling rain.

Formed with or like a rainbow.

See Reindeer.

A drop of rain.

A fall or descent of rain; the water, or amount of water, that falls in rain; as, the average annual rainfall of a region.

The state of being rainy.

Destitute of rain; as, a rainless region.

Abounding with rain; wet; showery; as, rainy weather; a rainy day or season.

A rope; also, a measure equal to a rod.

Same as 2d Reis.

Capable of being raised.

Lifted up; showing above the surroundings; as, raised or embossed metal work.

One who, or that which, raises (in various senses of the verb).

A grape, or a bunch of grapes.

The act of lifting, setting up, elevating, exalting, producing, or restoring to life.

Arranged systematically, or according to classes or subjects; as, a catalogue raisonn/. See under Catalogue.

A separator.

Reign; rule.

Same as Rajah.

A native prince or king; also, a landholder or person of importance in the agricultural districts.

The office or dignity of a rajah.

A Hindoo of the second, or royal and military, caste; a Kshatriya; especially, an inhabitant of the country of Rajpootana, in northern central India.

To walk about; to gad or ramble idly.

See Rake, a mineral vein.

A kind of ardent spirits used in southern Europe and the East, distilled from grape juice, grain, etc.

A lewd, dissolute fellow; a debauchee; a rake.

Dissolute; wild; lewd; rakish.

Hasty; reckless; rash.

One who, or that which, rakes A person who uses a rake. A machine for raking grain or hay by horse or other power. A gun so placed as to rake an enemy's ship.

Debauchery; lewdness.

A vile, dissolute wretch.

The handle of a rake.

The act or process of using a rake; the going over a space with a rake.

Having a saucy appearance indicative of speed and dash.

In a rakish manner.

The quality or state of being rakish.