dark matter(n = noun.substance) Array - (cosmology) a hypothetical form of matter that is believed to make up 90 percent of the universe; it is invisible (does not absorb or emit light) and does not collide with atomic particles but exerts gravitational force; Array
is a kind of matter
has parts: weakly interacting massive particle, wimp

N  darkness, absence of light, blackness, obscurity, gloom, murk, dusk, Cimmerian darkness, Stygian darkness, Egyptian darkness, night, midnight, dead of night, witching hour of night, witching time of night, blind man's holiday, darkness visible, darkness that can be felt, palpable obscure, Erebus, the jaws of darkness, sablevested night, shade, shadow, umbra, penumbra, sciagraphy, obscuration, occultation, adumbration, obumbration, obtenebration, offuscation, caligation, extinction, eclipse, total eclipse, gathering of the clouds, shading, distribution of shade, chiaroscuro, noctivagation, black body, hohlraum, black hole, dark star, dark matter, cold dark matter, dark, darksome, darkling, obscure, tenebrious, sombrous, pitch dark, pitchy, pitch black, caliginous, black, sunless, lightless &c (sun) (light), somber, dusky, unilluminated &c (illuminate), nocturnal, dingy, lurid, gloomy, murky, murksome, shady, umbrageous, overcast, cloudy, darkened, dark as pitch, dark as a pit, dark as Erebus, benighted, noctivagant, noctivagous, in the dark, in the shade, brief as the lightning in the collied night, eldest Night and Chaos, ancestors of Nature, the blackness of the noonday night, the prayer of Ajax was for light.

as a matter of fact, back matter, conservation of matter, crux of the matter, dark, dark adaptation, dark ages, dark blue, dark bread, dark chocolate, dark cloud, dark comedy, dark field illumination, dark glasses, dark ground illumination, dark horse, dark lantern, dark meat, dark red, end matter, faecal matter, fecal matter, for that matter, foul matter, front matter, gray matter, grey matter, grope in the dark, in the dark, law of conservation of matter, matter, matter of course, matter of fact, matter of law, matter to, minor matter, no matter, no matter what, no matter what happens, nontextual matter, particulate matter, pictorial matter, printed matter, reading matter, state of matter, subject matter, tabular matter, textual matter, vegetable matter, waste matter, white matter, written matter