Is it a common or proper noun birth certificate?

Answer 1

The noun 'baby' is a common, concrete noun.

A common noun is a general word for any person, place, or thing. The noun 'baby' is a general word for any very young offspring of a person or an animal.

An abstract noun is a word for something that can't be experienced by any of the five physical senses; something that can't be seen, heard, smelled, tasted, or touched. The noun 'baby' is a word for a physical person or thing, a concrete noun.

Answer 2

The term 'birth certificate' is a common noun. You may see these words capitalized on the top of the document because it is the title of that document.