Read the dictionary definition of dark. All definitions for this word.
1. an unenlightened state
1. he was in the dark concerning their intentions
2. his lectures dispelled the darkness
2. an unilluminated area
1. he moved off into the darkness
3. absence of light or illumination
4. absence of moral or spiritual values
1. the powers of darkness
5. the time after sunset and before sunrise while it is dark outside
6. not giving performances; closed
1. the theater is dark on Mondays
7. brunet (used of hair or skin or eyes)
1. dark eyes
8. devoid of or deficient in light or brightness; shadowed or black
1. sitting in a dark corner
2. a dark day
3. dark shadows
4. dark as the inside of a black cat
9. causing dejection
1. a blue day
2. the dark days of the war
3. a week of rainy depressing weather
4. a disconsolate winter landscape
5. the first dismal dispiriting days of November
6. a dark gloomy day
7. grim rainy weather
10. (used of color) having a dark hue
1. dark green
2. dark glasses
3. dark colors like wine red or navy blue
11. marked by difficulty of style or expression
1. much that was dark is now quite clear to me
2. those who do not appreciate Kafka's work say his style is obscure
12. lacking enlightenment or knowledge or culture
1. this benighted country
2. benighted ages of barbarism and superstition
3. the dark ages
4. a dark age in the history of education
13. stemming from evil characteristics or forces; wicked or dishonorable
1. black deeds
2. a black lie
3. his black heart has concocted yet another black deed
4. Darth Vader of the dark side
5. a dark purpose
6. dark undercurrents of ethnic hostility
7. the scheme of some sinister intelligence bent on punishing him
14. showing a brooding ill humor
1. a dark scowl
2. the proverbially dour New England Puritan
3. a glum, hopeless shrug
4. he sat in moody silence
5. a morose and unsociable manner
6. a saturnine, almost misanthropic young genius
7. a sour temper
8. a sullen crowd
15. secret
1. keep it dark