psychology An erroneous belief that is held in the face of evidence to the contrary.

synonym: psychotic belief.

Dutch: waanzin

A mistaken or unfounded opinion or idea:
— He has delusions of competence.

synonym: hallucination.

Roget 503: disordered reason, disordered intellect; diseased mind, unsound mind, abnormal mind; derangement, unsoundness; psychosis; neurosis; cognitive disorder; affective disorder^†.    insanity, lunacy; madness etc. adj.; mania, rabies, furor, mental alienation, aberration; paranoia, schizophrenia; dementation^†, dementia, demency^†; phrenitis^†, phrensy^†, frenzy, raving, incoherence, wandering, delirium, calenture of the brain^†; delusion, hallucination; lycanthropy^†; brain storm^†.    vertigo, dizziness, swimming; sunstroke, coup de soleil [Fr.], siriasis^†.    fanaticism, infatuation, craze; oddity, eccentricity, twist, monomania (caprice) 608; kleptodipsomania^†; hypochondriasis [Med.] etc. (low spirits) 837; melancholia, depression, clinical depression, severe depression; hysteria; amentia^†.    screw loose, tile loose, slate loose; bee in one's bonnet, rats in the upper story.    dotage etc. (imbecility) 499.    ... show more

Dutch: chimère, drogbeeld, fantasma, hallucinatie, hersenschim, hersenspinsel, illusie, spooksel, waan, waandenkbeeld, waanidee, waanvoorstelling, zinsbegoocheling ... show more
Polish: iluzja

The act of deluding; deception by creating illusory ideas.

synonyms: head game, illusion.

Roget 495: error, fallacy; misconception, misapprehension, misstanding^†, misunderstanding; inexactness etc. adj.; laxity; misconstruction etc. (misinterpretation) 523; miscomputation etc. (misjudgment) 481; non sequitur etc. 477; mis-statement, mis-report; mumpsimus^†.    mistake; miss, fault, blunder, quiproquo, cross purposes, oversight, misprint, erratum, corrigendum, slip, blot, flaw, loose thread; trip, stumble etc. (failure) 732; botchery etc. (want of skill) 699^†; slip of the tongue, slip of the lip, Freudian slip; slip of the pen; lapsus linguae [Lat.], clerical error; bull etc. (absurdity) 497; haplography^†.    illusion, delusion; snare; false impression, false idea; bubble; self-decit, self-deception; mists of error.    heresy etc. (heterodoxy) 984; hallucination etc. (insanity) 503; false light etc. (fallacy of vision) 443; dream etc. (fancy) 515; fable etc. (untruth) 546; bias etc. (misjudgment) 481; misleading etc. v.. ... show more

Roget 545: deception; falseness etc. 544; untruth etc. 546; imposition, imposture; fraud, deceit, guile; fraudulence, fraudulency^†; covin^†; knavery etc. (cunning) 702; misrepresentation etc. (falsehood) 544; bluff; straw-bail, straw bid [U.S.]; spoof [Slang].    delusion, gullery^†; juggling, jugglery^†; slight of hand, legerdemain; prestigiation^†, prestidigitation; magic etc. 992; conjuring, conjuration; hocus-pocus, escamoterie^†, jockeyship^†; trickery, coggery^†, chicanery; supercherie^†, cozenage^†, circumvention, ingannation^†, collusion; treachery etc. 940; practical joke.    trick, cheat, wile, blind, feint, plant, bubble, fetch, catch, chicane, juggle, reach, hocus, bite; card sharping, stacked deck, loaded dice, quick shuffle, double dealing, dealing seconds, dealing from the bottom of the deck; artful dodge, swindle; tricks upon travelers; stratagem etc. (artifice) 702; confidence trick, fake, hoax; theft etc. 791; ballot-box stuffing [U.S.], barney [Slang]; brace game [Slang], bunko game, drop game [Slang], gum game [U.S.], panel game [U.S.], shell game, thimblerig, skin game [U.S.].    snare, trap, pitfall, decoy, gin; springe^†, springle^†; noose, hoot; bait, decoy-duck, tub to the whale, baited trap, guet-a-pens; cobweb, net, meshes, toils, mouse trap, birdlime; dionaea^†, Venus's flytrap^†; ambush etc. 530; trapdoor, sliding panel, false bottom; spring-net, spring net, spring gun, mask, masked battery; mine; flytrap^†; green goods [U.S.]; panel house.    Cornish hug; wolf in sheep's clothing etc. (deceiver) 548; disguise, disguisement^†; false colors, masquerade, mummery, borrowed plumes; pattes de velours [Fr.].    mockery etc. (imitation) 19; copy etc. 21; counterfeit, sham, make-believe, forgery, fraud; lie etc. 546; a delusion a mockery and a snare" [Denman], hollow mockery.    whited sepulcher, painted sepulcher; tinsel; paste, junk jewelry, costume jewelry, false jewelry, synthetic jewels; scagliola^†, ormolu, German silver, albata^†, paktong^†, white metal, Britannia metal, paint; veneer; jerry building; man of straw.    illusion etc. (error) 495; ignis fatuus [Lat.] etc. 423; mirage etc. 443.    ... show more

Dutch: waan, inbeelding
Polish: mamienie, mylenie, zwodzenie, łudzenie