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PIE word

The verb is a learned borrowing from Medieval Latin irradiātus + English -ate (suffix forming verbs denoting ‘to act in the specified manner’). Irradiātus is the perfect passive participle of irradiō, from Latin ir- (a variant of in- (prefix meaning ‘against; into; on, upon’)) + radiō (to cause to radiate, irradiate; to emit beams, radiate) (from radius (ray of light; rod, staff; spoke of a wheel) (further etymology uncertain; possibly ultimately from Proto-Indo-European *reh₁t- (beam; pole; post)) + (suffix forming regular first-conjugation verbs)).[1][2]

The adjective is derived from Late Middle English irradiate (illuminated, shining),[3] borrowed from Medieval Latin irradiātus (see above) + Middle English -at (suffix forming past participles of verbs).[4] The adjective is attested earlier than the verb.[1][5]

The English word is analysable as ir- (prefix meaning ‘against; into; on, upon’) +‎ radiate.[6]



irradiate (third-person singular simple present irradiates, present participle irradiating, simple past and past participle irradiated)

  1. (transitive)
    1. To send out (heat, light, or some other form of radiation) in the form of rays; to radiate.
    2. (often literary or poetic) To make (someone or something) bright by shining light on them or it; to brighten, to illuminate.
      Synonyms: illumine, light up; see also Thesaurus:illuminate
    3. (technology) To apply radiation other than visible light to (someone or something).
      1. To treat (food) with ionizing radiation to destroy pathogens.
        • 1985 November 18, J. Richard Graves, jr., witness, “Statement of J. Richard Graves, jr., Chairman, Government Relations Committee, United Fresh Fruit and Vegetable Association”, in Federal Food Irradiation Development and Control Act of 1985: Hearing before the Subcommittee on Department Operations, Research, and Foreign Agriculture of the Committee on Agriculture, House of Representatives, Ninety-Ninth Congress, First Session on H.R. 696 [] (Serial No. 99-14), Washington, D.C.: U.S. Government Printing Office, published 1986, →OCLC, page 100:
          An inherent protection in labeling of the shipping containers will be the prevention of irradiating the commodity again, insuring that the produce has been treated within the safety limits established by the FDA [Food and Drug Administration].
      2. (medicine) To treat (a patient, or a cancerous growth or tumour) with radiation.
    4. (figurative, often literary or poetic)
      1. To animate or enliven (one's mood, or soul or spirit).
        • a. 1677 (date written), Matthew Hale, “Dangers that may Arise from Your Constitution and Complexion”, in A Letter of Advice to His Grandchildren, Matthew, Gabriel, Anne, Mary, and Frances Hale. [], Boston, Mass.: Wells and Lilly [], published 1817, →OCLC, page 35:
          [] I therefore beseech God to give you his grace and blessing, and the influence of his blessed Spirit, that you may subdue and conquer the temperament of your nature, to do all things well-pleasing to him, and that may irradiate and strengthen your souls and direct you in all things, for there is none that teacheth like him.
      2. To cause (one's face) to look beautiful, happy, or lively; to light up.
        • 1877, William Black, “Mid-Atlantic”, in Green Pastures and Piccadilly. [], volume II, London: Macmillan and Co., →OCLC, page 186:
          [W]e regarded with awe and reverence the sublime features of Madame Columbus, now irradiated with triumph.
      3. To decorate (a place) splendidly.
      4. To enlighten (someone, their mind, etc.) intellectually or spiritually; to illuminate, to shed light on.
        This book might irradiate your mind
        • a. 1711 (date written), George Bull, “Discourse III. Concerning the Spirit of God in the Faithful; []”, in Some Important Points of Primitive Christianity Maintained and Defended; in Several Sermons and Other Discourses, Oxford, Oxfordshire: John Henry Parker, published 1840, →OCLC, page 400:
          And indeed we ought, in these happy intervals, when our understandings are thus irradiated and enlightened, to make a judgment of the state and condition of our souls in the sight of God, and not to take our estimate of it when our understandings are eclipsed, and we are overshadowed with a dark cloud of sadness and melancholy.
        • 1799–1805 (dates written), William Wordsworth, “Book II. School-time.—(Continued.)”, in The Prelude, or Growth of a Poet’s Mind; an Autobiographical Poem, London: Edward Moxon, [], published 1850, →OCLC, page 43:
          For him, in one dear Presence, there exists / A virtue which irradiates and exalts / Objects through widest intercourse of sense.
        • 1838, [Letitia Elizabeth] Landon (indicated as editor), chapter XVI, in Duty and Inclination: [], volume II, London: Henry Colburn, [], →OCLC, page 227:
          Nevertheless, she seemed to him so new to life, so truly a child—a reason, doubtless, more urgent to uphold and lend her his protection: the ray of humanity irradiating her features—the exclamation that burst from her, upon his first arousing from the torpor of insensibility, whilst extended in his narrow hammock on ship-board, had ever since left impressions of gratitude on his memory.
        • 1839, Henry Hallam, “History of Physical and Other Literature from 1650 to 1700”, in Introduction to the Literature of Europe, in the Fifteenth, Sixteenth and Seventeenth Centuries, volume IV, London: John Murray, [], →OCLC, section V (On Geography and History), paragraph 48, page 604:
          He [Jacques-Bénigne Bossuet] first irradiated the entire annals of antiquity down to the age of Charlemagne with flashes of light that reveal an unity and coherence which had been lost in their magnitude and obscurity.
      5. To send out (something) as if in the form of rays; to diffuse, to radiate, to shed.
        • 1621, Democritus Junior [pseudonym; Robert Burton], “Starres a Cause. Signes from Physiognomy, Metoposcopy, Chiromancy”, in The Anatomy of Melancholy, [], Oxford, Oxfordshire: Printed by John Lichfield and Iames Short, for Henry Cripps, →OCLC, partition 1, section 2, member 1, subsection 4, page 75:
          Mercury in any geniture, if he ſhall be found in Virgo, or Piſces his oppoſite ſigne, and that in the Horoſcope, irradiated by thoſe quartile aspects of Saturne or Mars, the childe ſhall be mad or melancholy.
        • 1876 June, Henry James, Jr., chapter III, in The American, Boston, Mass.: James R[ipley] Osgood and Company, [], published 5 May 1877, →OCLC, pages 56–57:
          [H]is ideal of grandeur was a splendid façade, diffusing its brilliancy outward too, irradiating hospitality.
    5. (obsolete, figurative) To influence (something) as if with rays of heat, light, etc.
      • 1662, Bartholinus [i.e., Thomas Bartholin], “Of the Kidneys”, in Nicholas Culpeper and Abdiah Cole, transl., Bartholinus Anatomy; [] (The Physitian’s Library), London: [] Peter Cole [], →OCLC, 1st book (Of the Lower Belly), page 48, column 1:
        [T]he neighbouring Spermatick Veſſels are irradiated and virtuated by the kidneys, even as the Brain irradiates the lovver Parts, by an inbred property reſembling light.
      • a. 1677 (date written), Matthew Hale, “A Brief Consideration of the Hypotheses that Concern the Eternity of the World”, in The Primitive Origination of Mankind, Considered and Examined According to the Light of Nature, London: [] William Godbid, for William Shrowsbery, [], published 1677, →OCLC, section I, page 76:
        There muſt be antecedent to it that Ethereal or Solar heat, that muſt digeſt, influence, irradiate, and put theſe more ſimple parts of Matter into motion and coalition: []
  2. (intransitive, often literary or poetic)
    1. To become bright; to brighten, to light up.
    2. Often followed by on or upon: to emit rays of light; to shine.
    3. (figurative) To emit something other than light; to radiate.
      • 1733, Tho[mas] Allen, “Jesus Christ’s Sixth Royal Embassy; or Word to the Angel of the Church in Philadelphia”, in The Christian’s Sure Guide to Eternal Glory: Or, Living Oracles Most Comfortable, Holy and Instructive of the Lord Jesus Christ from Heaven, in His Royal Embassy to the Seven Churches of Asia, [], London: [] Francis Jefferies [], →OCLC, page 253:
        [T]he pleaſures of ſenſe have no reliſh vvhere thou [Jesus] irradiateſt and teſtifieſt vvith our conſcience, that vve are the children of God, and have done thy vvill ſincerely, []
    4. (obsolete) To diverge or be sent out in the form of rays.
      • a. 1705 (date written), [John Locke], “[Second Epistle of St. Paul to the Corinthians]”, in A Paraphrase and Notes on the Epistles of St. Paul [], London: [] J[ohn] H[umphreys] for Awnsham and John Churchill, [], published 1706, →OCLC, section II, footnote 6(y), page 21:
        [] Moſes by approaching to God in the Mount, had a Communication of Glory or Light from him, vvhich irradiated from his Face vvhen he deſcended from the Mount.


Derived terms[edit]

Related terms[edit]



irradiate (comparative more irradiate, superlative most irradiate) (literary or poetic)

  1. Made brilliant or bright; irradiated, illuminated.
  2. (figurative) Made splendid or wonderful.



  1. 1.0 1.1 irradiate, v. and adj.”, in Unabridged,, LLC, 1995–present, reproduced from Stuart Berg Flexner, editor in chief, Random House Unabridged Dictionary, 2nd edition, New York, N.Y.: Random House, 1993, →ISBN.
  2. ^ irradiate, v.”, in OED Online Paid subscription required, Oxford, Oxfordshire: Oxford University Press, December 2023.
  3. ^ irradiāte, adj.”, in MED Online, Ann Arbor, Mich.: University of Michigan, 2007.
  4. ^ -āt, suf.(1)”, in MED Online, Ann Arbor, Mich.: University of Michigan, 2007; compare “-ate, suf.2”, in OED Online Paid subscription required, Oxford, Oxfordshire: Oxford University Press, July 2023.
  5. ^ irradiate, adj.”, in OED Online Paid subscription required, Oxford, Oxfordshire: Oxford University Press, July 2023.
  6. ^ ir-, pref.1”, in OED Online Paid subscription required, Oxford, Oxfordshire: Oxford University Press, launched 2000; “ir-, pref.”, in Lexico,; Oxford University Press, 2019–2022.

Further reading[edit]


Etymology 1[edit]



  1. inflection of irradiare:
    1. second-person plural present indicative/subjunctive
    2. second-person plural imperative

Etymology 2[edit]


irradiate f pl

  1. feminine plural of irradiato





  1. second-person singular voseo imperative of irradiar combined with te