Helio is defined as something related to light, the sun, or sunlight.
An example of helio is Helios, the Greek sun god.
sun, sunlight, light: heliocentric, heliograph
Origin of helio-Classical Latin ; from Classical Greek h?lio- ; from h?lios, sun
Origin of helio-Greek hēlio-, from hēlios, sun; see sāwel- in Indo-European roots.