/sʌn/
[noun] The star at the centre of our solar system that gives light and heat to Earth. It is also used to describe the light and warmth that come from this star.
The word 'sun' is so ancient it connects us to a single Proto-Indo-European root shared by Sanskrit, Latin, and Greek — spoken before writing existed.
The word 'sun' reaches back further than almost any other word in the English language. Its ancestor is the Proto-Indo-European root *sóh₂wl̥ or *swen-, a word spoken by peoples living on the Eurasian steppes perhaps six thousand years ago, long before any writing system existed. This root spread outward with migrating populations across Europe and Asia, embedding itself into dozens of languages that would eventually grow quite distinct from one another — a remarkable act of linguistic preservation.
In the Germanic branch of that great language family, the root evolved into Proto-Germanic *sunnō, a feminine noun. This form passed directly into Old English as sunne, and you can hear the clear family resemblance in the modern German Sonne and Dutch zon. Old Norse had sól, and this too descended from the same ancient root. What is striking is that the earliest Germanic speakers treated the sun as grammatically feminine — a tradition preserved in German to this day, though English later lost its grammatical gender entirely.
The Latin branch followed a different path from the same Proto-Indo-European root, giving sol — the word the Romans used for the sun and the source of English words like solar, solstice (from Latin sol + sistere, meaning 'sun standing still'), and solarium. Greek developed hḗlios from a related root, which travelled into English through scientific vocabulary as heliocentric, helium (the element first discovered in the sun's spectrum), and heliograph. These are cousins of 'sun', not identical twins, but they all share that ancient ancestor.
Sanskrit, another descendant of Proto-Indo-European, preserved the root as sūrya, the name of the sun deity in Hindu tradition. The fact that an English farmer saying 'sun' and a Sanskrit scholar saying sūrya are using words from the same prehistoric source is one of the most quietly astonishing facts in the history of human language. Linguists reconstructed this common origin not because anyone recorded it, but because the patterns of sound change are so consistent and predictable across languages that the family tree can be traced backward with remarkable confidence.
By the time Old English sunne reached Middle English, it had simplified to sonne and then gradually to the modern form sun. The spelling shifted, the grammatical gender was lost, but the core sound — that open, warm vowel — persisted with barely a murmur of change across millennia. It is also worth noting that the word 'Sunday' preserves a direct tribute to the sun: it comes from Old English sunnandæg, meaning 'day of the sun', a translation of the Latin dies Solis, which itself was a translation of a Babylonian system of naming days after celestial bodies. Every time someone says the word Sunday, they are unknowingly reciting a chain of reverence for the sun that goes back to ancient Mesopotamia.