heli- I. combining form orhelio- Etymology: Latin, from Greek hēli-, hēlio-, from hēlios — more at solar : sun < Heliornis > : the sun < heliocentric > < helioscope > : sunlight : solar energy < heliogravure > : sun and < heliolithic > II. combining form Etymology: by shortening : helicopter < heliport > < helimail >