Extended Strong's Greek Lexicon (Abbott-Smith based)
darkness
Usage: γνόφος (later form of δν-), [in LXX for אָפֵל, עֲרָפֶל, etc. ;] darkness, gloom (including "an element of tempest," Tr., Syn., §with): Heb.12:18.† SYN.: ἀχλύς, ζόφος, σκότος (Tr., l.with; DB, i, 457a). (AS)