Why sky is common noun?

Answer 1

The noun 'sky' is a common noun because a common noun is a word for any person, place, thing, or idea. A proper noun is a word for a specific person, place, thing, or a title, for example, Sky Murphy, the Sky Hotel is Aspen Colorado, or the movie title 'Vanilla Sky'.

Answer 2

"Sky" is considered a common noun because it refers to a general, non-specific thing, rather than a particular or unique sky. It is a word used to describe the atmosphere above us.