dark

Etymology 1

From Middle English derk, from Old English deorc, from Proto-West Germanic *derk (“dark”), of uncertain origin, but possibly from Proto-Indo-European *dʰerg- (“dim, dull”), from Proto-Indo-European *dʰer- (“dull, dirty”).

adj

1. Having an absolute or (more often) relative lack of light.
   1. (of a source of light) Extinguished.
      Dark signals should be treated as all-way stop signs.
   2. Deprived of sight; blind.
2. Transmitting, reflecting, or receiving inadequate light to render timely discernment or comprehension: caliginous, darkling, dim, gloomy, lightless, sombre.
3. (of colour) Dull or deeper in hue; not bright or light.
   my sister's hair is darker than mine;  her skin grew dark with a suntan
4. Ambiguously or unclearly expressed: enigmatic, esoteric, mysterious, obscure, undefined.
   the dark problems of existence 1881, John Shairp, Aspects of Poetry
5. Marked by or conducted with secrecy: hidden, secret; clandestine, surreptitious.
   Clarence, can you lend me three thousand pounds on good security and keep it dark from Connie? 1923, P. G. Wodehouse, chapter I, in Leave It to Psmith
   The first favourite was never heard of, the second favourite was never seen after the distance post, all the ten-to-oners were in the rear, and a dark horse which had never been thought of, and which the careless St. James had never even observed in the list, rushed past the grand stand in sweeping triumph. (gambling, of race horses) Having racing capability not widely known. 1831, Benjamin Disraeli, The Young Duke — a moral tale though gay
6. Without moral or spiritual light; sinister, malign.
   a dark villain;  a dark deed
7. Conducive to hopelessness; depressing or bleak.
   the Great Depression was a dark time;  the film was a dark psychological thriller
8. (of a time period) Lacking progress in science or the arts.
   The age wherein he lived was dark, but he Could not want light who taught the world to see. 1668, John Denham, The Progress of Learning
9. Extremely sad, depressing, or somber, typically due to, or marked by, a tragic or undesirable event.
   September 11, 2001, the day when four terrorist attacks destroyed the Twin Towers and the Pentagon, is often referred to as America's dark day.
   April 1, 2014, “Marathon Mementos Remind of Boston's Dark Day”, in NBC News:
10. With emphasis placed on the unpleasant aspects of life; said of a work of fiction, a work of nonfiction presented in narrative form, or a portion of either.
    The ending of this book is rather dark.
11. (broadcasting, of a television station) Off the air; not transmitting.

Etymology 2

From Middle English derk, derke, dirke, dyrke, from the adjective (see above), or possibly from an unrecorded Old English *dierce, *diercu (“dark, darkness”).

noun

1. A complete or (more often) partial absence of light.
   Dark surrounds us completely.
   The face which emerged was not reassuring. It was blunt and grey, the nose springing thick and flat from high on the frontal bone of the forehead, whilst his eyes were narrow slits of dark in a tight bandage of tissue. […]. 1963, Margery Allingham, chapter 17, in The China Governess
   [Rural solar plant] schemes are of little help to industry or other heavy users of electricity. Nor is solar power yet as cheap as the grid. For all that, the rapid arrival of electric light to Indian villages is long overdue. When the national grid suffers its next huge outage, as it did in July 2012 when hundreds of millions were left in the dark, look for specks of light in the villages. 2013-07-20, “Out of the gloom”, in The Economist, volume 408, number 8845
2. (uncountable) Ignorance.
   We kept him in the dark.
   The lawyer was left in the dark as to why the jury was dismissed.
   Till we perceive it by our own understandings, we are as much in the dark, and as void of knowledge, as before.
3. (uncountable) Nightfall.
   It was after dark before we got to playing baseball.
4. A dark shade or dark passage in a painting, engraving, etc.

Etymology 3

From Middle English derken, from Old English deorcian, from Proto-West Germanic *derkōn.

verb

1. (intransitive) To grow or become dark, darken.
2. (intransitive) To remain in the dark, lurk, lie hidden or concealed.
   To dark is still used in Swaledale (Yorkshire) in the sense of to lie hid, as, 'Te rattens [rats] mun ha bin darkin whel nu [till now]; we hannot heerd tem tis last fortnith'. 1873, Richard Morris, Walter William Skeat, “Glossarial Index”, in Specimens of Early English, volumes II: From Robert of Gloucester to Gower, A.D. 1298—A.D. 1393, Oxford: Clarendon Press, page 490
3. (transitive) To make dark, darken; to obscure.