| R |
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noun - The eighteenth letter of the Appendix:Roman script, English alphabet, preceded by Q and followed by S.
abbreviation - (context, US politics) Republican
- (film certification) restricted
- reverse
- right (as opposed to left)
- (context, handbells) ring
- (context, baseball, cricket) The statistic reporting the number of runs scored by a player
- Thursday
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| rad |
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noun
- (metrology) A non-SI unit of absorbed dose of radiation, equal to 0.01 gray.
adjective
- (slang) excellent, short for radical
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| radiant |
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noun
- A point source from which radiation is emitted.
- (astronomy) The apparent origin, in the night sky, of a meteor shower.
adjective
- Radiate, Radiating light and/or heat.
- Emitted as radiation.
- Bright, glowing or filled with light.
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| radiate |
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verb (radiat, ing)
- To extend, send or spread out from a center like radii.
- (transitive) To emit rays or waves.
- The stove radiates heat.
- (intransitive) To come out or proceed in rays or waves.
- The heat radiates from a stove.
- (transitive) To illuminate.
- To expose to ionizing radiation, such as by radiography.
- (transitive) To manifest oneself in a glowing manner.
- (context, ecology, intransitive) to spread into new habitats, migrate.
adjective
- radiating from a center.
- surrounded by rays, such as the head of a saint in a religious picture.
- (botany) having parts radiating from the center, such as the petals in many flowers.
- (biology) having radial symmetry, such as a seastar.
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| radiation |
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noun
- The shooting forth of anything from a point or surface, like the diverging rays of light; as, the radiation of heat.
- The process of radiating waves or particles.
- The transfer of energy via radiation (as opposed to convection or conduction)
- Radioactive energy
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| radiation pressure |
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noun - (physics) the pressure exerted by electromagnetic radiation on an object on which it impinges, as a consequence of its momentum
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| radiative |
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adjective
- (physics) of, relating to, or occuring through radiation
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| radio |
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noun
- (uncountable) The technology that allows for the transmission of sound or other signals by modulation of electromagnetic waves.
- (countable) A device that can capture (receive) the signal sent over radio waves and render the modulated signal as sound.
- (countable) A device that can transmit radio signal.
verb
- To send a message by radio
- ''I think the boat is sinking, we'd better radio for help.
- Usage note: Used for small radio transmitters carried by people, ships, etc, not for regular radio broadcasting to large audiences.
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| radioactive |
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adjective
- Exhibiting radioactivity.
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| radioactivity |
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noun
- Spontaneous emission of radiation as a consequence of a nuclear reaction, or directly from the breakdown of an unstable nucleus.
- The radiation so emitted; including gamma rays, alpha particles, neutrons, electrons, positrons, etc.
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| radioluminescence |
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noun
- luminescence produced by bombardment with ionizing radiation
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| radionuclide |
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noun - (physics) a radioactive nuclide
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| range |
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noun
- Line or series of mountains.
- Large fuel-burning stove.
- Selection, array. Eg: A range of cars.
- Area used for shooting, artillery, etc.
- An area of open, often unfenced, grazing land.
- (mathematics) The set of values (points) which a function can obtain.
- (statistics) The length of the smallest interval which contains all the data. It is calculated by subtracting the smallest observations from the greatest.
- The distance to a target, or to the subject of discussion.
- We could see the ship at a range of five miles.
- (sports) (baseball) The defensive area that a player can cover.
- Jones has good for a big man.
- (music) Compass - The scale of all the tones a voice or an instrument can produce.
- (ecology) The geographical area or zone where a species is normally naturally found.
verb (ranges, ranging, ranged)
- (intransitive) (followed by over) To travel over (an area, etc) with a particular purpose.
- (intransitive) (mathematics, computing; followed by over) Of a variable, to be able to take any of the values in a specified range.
- The variable x ranges over all real values from 0 to 10.
- (transitive) classify
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| rarefaction |
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noun
- a reduction in the density of a material, especially that of a fluid
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| rarefy |
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verb to rarefy
- To make rare, thin, porous, or less dense
- To expand or enlarge without adding any new portion of matter to.
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| reactance |
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noun (symbol X)
- (context, physics, electric) opposition to the change in flow of current in an alternating current circuit, due to inductance and capacitance; the imaginary part of the impedance
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| reaction |
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noun
- An action or statement in response to a stimulus or other event
- The announcement of the verdict brought a violent .
- You were in the coutroom. What is your ?
- When I last tried to eat strawberries I had a terrible allergic .
- (chemistry) A transformation in which one or more substances is converted into another by combination or decomposition
- In this , the acid and base will neutralize each other, producing a salt.
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| recoil |
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noun
- (context, firearms) The amount of energy transmitted back to the shooter from a firearm which has fired. Recoil is a function of the weight of the weapon, the weight of the projectile, and the speed at which it leaves the muzzle.
verb (recoils, recoiling, recoiled)
- To pull back, especially in disgust, horror or astonishment.
- He recoiled in disgust when he saw the mess.
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| Red |
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noun
- A Communist
adjective
- Communist
- the Army
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| regenerate |
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verb (regenerat, ing)
- (transitive) To construct or create anew, especially in an improved manner
- (transitive) To revitalize
- (context, transitive, biology) To replace lost or damaged tissue
- (intransitive) To become reconstructed
- (intransitive) To undergo a spiritual rebirth
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| relative density |
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noun
- (science)A measure of the density of a material. The ratio of the density of a substance to the density of water at the same temperature. It is dimensionless and therefor has no units.
- Typical relative densities (approximate)
- : ethanol: 0.79
- : water: 1.00
- : iron: 7.8
- : gold: 19.3
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| relativistic mass |
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noun - (physics) the increased mass of an object moving at relativistic speed relative to an observer
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| relativity |
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noun
- the state of being relative to something else.
- (physics) the principle (due to Galileo) that the laws of physics should be the same for all observers in uniform motion.
- (physics) either of the two principles of special relativity or general relativity (Einstein, Albert Einstein).
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| repulsion |
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noun
- the act of repelling or the condition of being repelled
- an extreme dislike of something, or hostility to something
- (physics) the repulsive force acting between bodies of the same electric charge or magnetic polarity
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| repulsive |
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adjective
- tending to rouse aversion or to repulse
- (context, physics) having the capacity to repel
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| residence time |
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noun
- (hydrology) The average time a particular molecule of water will remain in a body of water.
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| restitution |
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noun
- a process of compensation for losses.
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| rest mass |
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noun - (physics) the mass of a body when it is not moving relative to an observer
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| reverberation |
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noun - A violent oscillation or vibration
- The discomfort caused by the bat's surprised Tommy.
- An echo, or a series of overlapping echos
- The that followed Marylin's shout filled the cavern.
- An evolving series of effects resulting from a particular event; a repercussion
- Reverberations from the Vietnam war affect our society to this day.
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| rheology |
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noun
- (physics) The branch of physics that studies the deformation and flow of matter.
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| roentgenoscope |
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noun
- a fluoroscope
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| Rydberg |
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proper noun
- a surname of Swedish origin, derived from ryd, woodland clearing + berg, mountain
- w:Johannes Rydberg, Johannes Rydberg Swedish physicist
- a lunar impact crater that is located on the far side of the Moon
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