Why is the nearest star specifically named 'the Sun' rather than just 'a star'?

Answer

It is a historical designation rooted in its proximity and governance of our days

The term 'Sun' is a proper noun stemming from history when it was viewed as the unique celestial body governing daylight. If it orbited another star, it would likely use a catalog designation.

Why is the nearest star specifically named 'the Sun' rather than just 'a star'?
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