IPA: /ˈdɑrkɪst/
KK: /dɑrkɪst/
The most lacking in light; the deepest shade or color.
The night sky was the darkest I had ever seen, filled with countless stars.
Comparative: darker
Superlative: darkest
Darkest → It is formed from "dark" (from Old English *deorc*, meaning lacking light or brightness) and "-est" (a superlative suffix indicating the highest degree). The word "darkest" means having the least light or being the most devoid of brightness.
Think of the Old English word for lacking light — that's what 'dark' means, and adding '-est' shows it's the most of that quality, making 'darkest' the most lacking in light.