as a deity. The synodic rotation of Earth and its orbit around the Sun are the basis of some solar calendars. The predominant calendar in use today is the Gregorian calendar which is based upon the standard 16th-century interpretation of the Sun's observed movement as actual movement. Etymology The English word sun developed from Old English . Cognates appear in other Germanic languages, including West Frisian , Dutch , Low German , Standard German , Bavarian , Old Norse , and Gothic . All these words stem from Proto-Germanic . This is ultimately related to the word for sun in other branches of the Indo-European language family, though in most cases a nominative stem with an l is found, rather than the genitive stem in n, as for example in Latin , ancient Greek (), Welsh and Czech , as well as (with *l > r) Sanskrit () and Persian (). Indeed, the l-stem survived in Proto-Germanic as well, as , which gave rise to Gothic (alongside ) and Old Norse prosaic (alongside poetic ), and through it the words for sun in the modern Scandinavian languages: Swedish and Danish , Icelandic , etc. The principal adjectives for the Sun in English are sunny for sunlight and, in technical contexts, solar (), from Latin – the latter found in terms such as solar day, solar eclipse and Solar System (occasionally Sol system). From the Greek comes the rare adjective heliac (). In English, the Greek and Latin words occur in poetry as personifications of the Sun, Helios () and Sol (), while in science fiction Sol may be used as a name for the Sun to distinguish it from other stars. The term sol with a lower-case s is used by planetary astronomers for the duration of a solar day on another planet such as Mars. The English weekday name Sunday stems from Old English "sun's day", a Germanic interpretation of the Latin phrase , itself a translation of the ancient Greek () 'day of the sun'. The astronomical symbol for the Sun is a circle with a center dot, . It is used for such units as M☉ (Solar mass), R☉ (Solar radius) and L☉ (Solar luminosity). General characteristics The Sun is a G-type main-sequence star that constitutes about 99.86% of the mass of the Solar System. The Sun has an absolute magnitude of +4.83, estimated to be brighter