Used as a noun or na-adjective for dark colors, atmospheres, themes, or moods. Common in compounds like ダークスーツ (dark suit) or ダークな雰囲気 (dark atmosphere).
彼はダークな色の服を好む。
He prefers dark-colored clothes.
This movie's dark atmosphere is its appeal.
その映画はダークな雰囲気が漂っている。
That movie has a dark atmosphere.
ダーク系の服を選ぶと落ち着いた印象になる。
Choosing dark-toned clothes gives a calm impression.
ブラック names the actual color black, whereas ダーク describes deep or muted shades of any color as well as gloomy themes, so they overlap but aren't identical.
dark matter
dark horse
dark web
dark elf
dark gray; dark grey
dark side
dark store; online-only retail outlet
dark suit
darknet; dark net
Loanword from English 'dark'.
dark blue
dark pool; dark liquidity
after-dark clothing; evening wear
dark green