1. (n.) An array of light waves, including red, orange, yellow, green, blue, indigo, and violet\; the several colored and other rays of which light is composed, separated by the refraction of a prism or other means, and observed or studied either as spread out on a screen, by direct vision, by photography, or otherwise. See Spectroscope.

2. (n.) An apparition; a specter.

3. (n.) A luminous appearance, or an image seen after the eye has been exposed to an intense light or a strongly illuminated object. When the object is colored, the image appears of the complementary color, as a green image seen after viewing a red wafer lying on white paper. Called also ocular spectrum.

AF CPS Dalmatian EHF HF Hz Indian file MF Maxwell triangle Munsell scale RF SHF UHF VHF VLF afterimage antigorite array articulation audio frequency bank bogey butterfly buzz candy cane carrier frequency carry catena catenation chain chain reaction chaining chameleon cheetah chromatic circle chromatic spectrum chromaticity diagram chrysotile color circle color cycle color index color mixture curve color solid color spectrum color system color triangle compass complementary color concatenation confetti connection consecution continuum course crazy quilt cycle cycles demitint descent diapason drone eidolon endless belt endless round extremely high frequency file filiation firedog frequency frequency spectrum full color fundamental colors gamut ghost gradation half tint halftone harlequin haunt hertz high frequency hue cycle hum intermediate frequency iris jaguar kilocycles kilohertz leopard line lineage low frequency lower frequencies mackerel mackerel sky marble marbled paper medium frequency megacycles megahertz metamer moire monochrome monotone mother-of-pearl nacre nexus ocelot ocular spectrum opal ophite optical illusion patchwork quilt peacock pendulum periodicity phantasm plenum powder train primary primary color progression pure color queue radio frequency radius rainbow range rank reach recurrence register reticulation revenant rotation round routine row run scale scope secondary secondary color sequence series serpentine serpentine marble shade shot silk single file solar spectrum spark frequency spectral color spectrum color spirit spook stretch string succession superhigh frequency swath sweep tertiary tertiary color thread tier tortoise shell train trick of eyesight ultrahigh frequency upper frequencies very high frequency very low frequency windrow zebra