A complete or (more often) partial absence of light.
"The sudden power outage plunged the entire room into dark, leaving us unable to see anything beyond a few inches in front of our faces."
In plain English: Dark is the state of having no light at all.
"The dark was so heavy that we could barely see our hands in front of us."
Usage: Use "dark" as a noun to describe a place where there is little or no light, such as walking into the dark after sunset. It refers to the condition of darkness itself rather than describing an object's color.
To grow or become dark, darken.
"The sky began to darken just before sunset."
In plain English: To make something dark is to cover it so no light can get through.
"The clouds darkened before the storm broke."
Usage: Use "darken" to describe something gradually changing color to black or becoming dimmer, rather than using it as a transitive verb to mean "to make dark." For example, say the clouds will darken before a storm instead of saying they will dark the sky.
devoid of or deficient in light or brightness; shadowed or black
"sitting in a dark corner"
"a dark day"
"dark shadows"
"dark as the inside of a black cat"
(used of color) having a dark hue
"dark green"
"dark glasses"
"dark colors like wine red or navy blue"
stemming from evil characteristics or forces; wicked or dishonorable
"black deeds"
"a black lie"
"his black heart has concocted yet another black deed"
"Darth Vader of the dark side"
"a dark purpose"
"dark undercurrents of ethnic hostility"
"the scheme of some sinister intelligence bent on punishing him"
showing a brooding ill humor
"a dark scowl"
"the proverbially dour New England Puritan"
"a glum, hopeless shrug"
"he sat in moody silence"
"a morose and unsociable manner"
"a saturnine, almost misanthropic young genius"
"a sour temper"
"a sullen crowd"
Having an absolute or (more often) relative lack of light.
"The basement was so dark that I had to turn on a flashlight just to find the switch for the lights."
Extinguished.
"After the power outage, he fumbled for a match to light his cigarette in the dark room."
In plain English: Dark describes something that has no light and is hard to see.
"The room became dark when the lights went out."
Usage: Use dark to describe something that has little or no light, such as a room at night or a shadowed corner. It also applies to objects that absorb most visible light and appear black or deep in color.
A surname.
"My neighbor, who has a dog named Dark, always greets me in the morning."
The word "dark" entered English from Middle English and Old English forms of uncertain origin. It may ultimately trace back to a Proto-Indo-European root meaning "dim" or "dull."