The Greek ἥλιος is the inherited word for the Sun, from Proto-Indo-European *seh₂u-el, which is cognate with Latin sol, Sanskrit surya, Old English swegl, Old Norse sól, Welsh haul, Avestan hvar, etc. The name Helen is thought to share this etymology, and may express an early alternate personification of the sun among Hellenic peoples.
The female offspring of Helios were called Heliades. The Greek sun god had various bynames or epithets, which over time in some cases came to be considered separate deities associated with the Sun. Most notably, Helios is closely associated with, and sometimes consciously identified with, Apollo.
Among these is Hyperion (superus, "high up"), Elektor (of uncertain derivation, often translated as "beaming" or "radiant", especially in the combination elektor Hyperion), Phaëton "the radiant", Hekatos (of Apollo, also Hekatebolos "far-shooter", i.e. the sun's rays considered as arrows).
Diodorus Siculus of Sicily reported that the Chaldeans called Cronus (Saturn) by the name Helios, or the sun, and he explained that this was because Saturn was the most conspicuous of the planets.