Bioluminescence is a noun that refers to the ability to naturally glow. 

Our word of the day comes from two Latin words, ‘bio’ (BEE oh), meaning ‘life,’ and ‘lumin,’ (LOO men) which means ‘light.’ Its descendent, bioluminescence has been around since the early 20th century describing a wide array of glowing creatures. Here’s an example:

Bugs that can glow in the dark have often creeped me out, but when I get lost in the woods, I’m happy to have them around. Without the bioluminescence of my tiny friends, I might get lost in the dark.