Dank and dark are easily confused words.
The spell-check application of most word processing software programs would not catch a slip-up of these two words. Spell-check is looking for words that aren’t in its dictionary, and words that resemble words in its dictionary but are possibly spelled wrong. Spell-check isn’t perfect. It doesn’t know and can’t guess what word you wanted or what word you meant, it can only judge the words on the page. If you used words that are all spelled correctly, it gives you a pass anyway.
Autocorrect suggests words that start with the same letters. It’s suggesting what word you may want to save time, but quite often, its suggestions are pretty off base. They don’t help you out, but they do make you laugh.
Dank is an adjective. It means to smell moldy or rotted. Typically a house after flooding will develop a dank odor if it is not cleaned up and allowed to dry out.
Dank also has a slang meaning (2000s+) as a highly potent marijuana cigarette. This meaning has been used to describe other things. If someone describes something as “dank” with positive connotations, they mean something is powerful, high quality, incredible, etc. [A similar phenomenon happened in the 1980s slang when “bad” would actually mean something cool or amazing.] (thanks to a twitter follower for bringing this meaning to my attention.)
Dark is an adjective. It describes a space where there is no light, and very little visibility. It can also describe a color that is closer to black than it is to white.
The following story uses both words correctly:
Danielle was an antiques collector and appraiser, so she was accustomed to finding treasures in dark attics and dank spaces. She also restored damaged pieces in her spare time.
Kathleen W Curry 