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noun ra·di·a·tion \ˌrā-dē-ˈā-shən\

Simple Definition of radiation

  • : a type of dangerous and powerful energy that is produced by radioactive substances and nuclear reactions

  • medical : the use of controlled amounts of radiation for the treatment of diseases (such as cancer)

  • : energy that comes from a source in the form of waves or rays you cannot see

Source: Merriam-Webster's Learner's Dictionary

Full Definition of radiation

  1. 1 a :  the action or process of radiating b :  the process of emitting radiant energy in the form of waves or particles c (1) :  the combined processes of emission, transmission, and absorption of radiant energy (2) :  the transfer of heat by radiation — compare conduction, convection

  2. 2 a :  something that is radiated b :  energy radiated in the form of waves or particles

  3. 3 :  radial arrangement

  4. 4 :  adaptive radiation


play \-shnəl, -shə-nəl\ adjective


play \-shən-ləs\ adjective


play \ˈrā-dē-ˌā-tiv\ adjective

Examples of radiation in a sentence

  1. She was exposed to high levels of radiation.

  2. He goes in for radiation next week.

  3. the sun's radiation of heat

15th Century

First Known Use of radiation

15th century

Rhymes with radiation

abdication, aberration, abjuration, abnegation, abrogation, acceptation, acclamation, accusation, activation, adaptation, adjuration, admiration, adoration, adulation, adumbration, affectation, affirmation, aggravation, aggregation, agitation, allegation, allocation, amputation, alteration, altercation, animation, annexation, annotation, appellation, application, approbation, arbitration, arrogation, aspiration, assignation, attestation, augmentation, automation, aviation, avocation, blaxploitation, botheration, calculation, calibration, cancellation, carbonation, castigation, celebration, cerebration, chlorination, circulation, cogitation, collocation, coloration, combination, comfort station, commendation, commutation, compensation, complication, computation, concentration, condemnation, condensation, confirmation, confiscation, conflagration, conformation, confrontation, congregation, conjugation, connotation, consecration, conservation, consolation, constellation, consternation, constipation, consultation, consummation, contemplation, conurbation, conversation, convocation, copulation, coronation, corporation, correlation, corrugation, crenellation, crop rotation, culmination, cultivation, cumulation, cybernation, decimation, declamation, declaration, declination, decoration, dedication, defamation, defecation, deformation, degradation, dehydration, delectation, delegation, demarcation, demonstration, denigration, denotation, depilation, deportation, depravation, depredation, deputation, derivation, derogation, desecration, designation, desolation, desperation, destination, detestation, detonation, devastation, deviation, dislocation, dispensation, disputation, dissertation, dissipation, distillation, divination, domination, education, elevation, elongation, emanation, embarkation, embrocation, emendation, emigration, emulation, enervation, escalation, estimation, evocation, exaltation, excavation, excitation, exclamation, exculpation, execration, exhalation, exhortation, exhumation, expectation, expiation, expiration, explanation, explication, exploitation, exploration, exportation, expurgation, extirpation, exultation, fabrication, fascination, federation, fenestration, fermentation, fibrillation, figuration, filling station, fire station, flagellation, fluoridation, fluctuation, forestation, formulation, fornication, fragmentation, fulmination, fumigation, gene mutation, generation, germination, glaciation, graduation, granulation, gravitation, habitation, hesitation, hibernation, hyphenation, ideation, imitation, immigration, immolation, implantation, implication, importation, imprecation, imputation, incantation, incarnation, inclination, incrustation, incubation, indentation, indication, indignation, infestation, infiltration, inflammation, information, inhalation, innovation, inspiration, installation, instigation, insulation, integration, intimation, intonation, inundation, invitation, invocation, irrigation, irritation, iteration, jubilation, laceration, lamentation, lamination, legislation, levitation, liberation, limitation, lineation, liquidation, litigation, lubrication, lucubration, maceration, machination, malformation, masturbation, maturation, mediation, medication, meditation, melioration, menstruation, ministration, mitigation, moderation, modulation, molestation, motivation, mutilation, navigation, nomination, obfuscation, objurgation, obligation, observation, occupation, operation, orchestration, ordination, oscillation, osculation, ostentation, ovulation, oxidation, pagination, palpitation, penetration, percolation, perforation, permeation, permutation, perpetration, perspiration, perturbation, pigmentation, pixilation, police station, pollination, population, postulation, power station, predication, preparation, presentation, preservation, proclamation, procreation, profanation, prolongation, promulgation, propagation, prorogation, protestation, provocation, publication, punctuation, recantation, recitation, reclamation, re-creation, recreation, reformation, refutation, registration, regulation, rehydration, relaxation, relocation, renovation, reparation, replication, reprobation, reputation, reservation, resignation, respiration, restoration, retardation, revelation, revocation, ruination, rumination, rustication, salutation, sanitation, saturation, segmentation, segregation, separation, sequestration, service station, sexploitation, simulation, situation, speciation, speculation, spoliation, stimulation, stipulation, strangulation, structuration, stylization, subjugation, sublimation, suffocation, syncopation, syndication, tabulation, termination, T formation, titillation, toleration, transfer station, transformation, translocation, transmigration, transmutation, transpiration, transplantation, transportation, trepidation, tribulation, ulceration, ululation, undulation, urination, vaccination, vacillation, validation, valuation, variation, vegetation, veneration, ventilation, vindication, violation, visitation, weather station

RADIATION Defined for Kids


noun ra·di·a·tion \ˌrā-dē-ˈā-shən\

Definition of radiation for Students

  1. 1 :  the process of giving off energy in the form of waves or particles

  2. 2 :  something that is radiated (as light or X-rays)

Medical Dictionary


noun ra·di·a·tion \ˌrād-ē-ˈā-shən\

Medical Definition of radiation

  1. 1:  energy radiated in the form of waves or particles

  2. 2a:  the action or process of radiating <with radiation of the pain there may be tenderness over the sciatic nerve—J. A. Key>b (1):  the process of emitting radiant energy in the form of waves or particles (2):  the combined processes of emission, transmission, and absorption of radiant energy

  3. 3:  a tract of nerve fibers within the brain; especially :  one concerned with the distribution of impulses arising from sensory stimuli to the relevant coordinating centers and nuclei <the optic radiations>

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