The best way to learn proper English is to read news report, and watch news on TV. Watching TV shows is a great way to learn casual English, slang words, understand culture reference and humor. If you have already watched these shows then you may recall the words used in the following dialogs.

you're getting caught up on the
ways I'm not like DARK matter.
The Big Bang Theory Season 11, Episode 10

That's what we are,
ghosts waiting for you in the DARK.
Game of Thrones Season 3, Episode 4

You're lost in the DARK.
Westworld Season 2, Episode 7

AMY:
Wow, this is really DARK.
The Big Bang Theory Season 12, Episode 19

...the DARK matter signal found
in sodium-iodide crystals by the Italians.
The Big Bang Theory Season 2, Episode 15