solar

Solar comes from Late Middle English solar, borrowed from Latin sōlāris, an adjective built from sōl, meaning 'sun.' That Latin root itself traces back to the Proto-Indo-European *sóh₂wl̥, an ancient word for the sun.

The word entered English already meaning 'of or relating to the sun,' following the sense of its Latin source closely, without any major shift recorded here.

Because it comes from Latin sōl, solar shares its root with other sun-words descended from the same PIE base, though only sōl itself is named in this history.