Abarim Publications' online Biblical Hebrew Dictionary
The verb נגה (nagah) means to lighten, or to reflect light and occurs a mere two or three times in the Bible: 2 Samuel 22:29, which is reduplicated as Psalm 18:28 ("lighten up the darkness"), and Isaiah 13:10 ("the moon reflects light").
It's probably prudent to note that this root does not actually describe light or being light (which would be done with the root אור, 'or) but rather the traveling of light or else its effect of illuminating.
From this verb come the following two derivatives:
- The feminine noun נגה (nogah), meaning brightness (Amos 5:20, Proverbs 4:18), a lightening up (Isaiah 60:3), or the reflecting of light (Isaiah 60:13, Habakkuk 3:11).
- The feminine noun נגהה (negoha), also meaning brightness (Isaiah 59:9 only).