The English proper noun Sun developed from Old English sunne and may be related to south. Cognates to English sun appear in other Germanic languages, including Old Frisian sunne, sonne, Old Saxon sunna, Middle Dutch sonne, modern Dutch zon, Old High German sunna, modern German Sonne, Old Norse sunna, and Gothic sunnō. All Germanic terms for the Sun stem from Proto-Germanic *sunnōn.
The English weekday name Sunday stems from Old English (Sunnandæg; “Sun’s day”, from before 700) and is ultimately a result of a Germanic interpretation of Latin dies solis, itself a translation of the Greek ἡμέρα ἡλίου (hēméra hēlíou). The Latin name for the Sun, Sol, is widely known but is not common in general English language use; the adjectival form is the related word solar. The term sol is also used by planetary astronomers to refer to the duration of a solar day on another planet, such as Mars. A mean Earth solar day is approximately 24 hours, whereas a mean Martian ‘sol’ is 24 hours, 39 minutes, and 35.244 seconds. Read more