Could you please differentiate a common noun, from a concrete noun?
I believe common nouns to be, for example 'computer', 'sandwich', 'cats' etc...
However I also understand that concrete nouns are those which have a physical/solid property, such as 'watch', 'clock' and 'tree'.
I can't believe that I only did A-Level English 6 years ago!
A common noun is a broad category that includes nouns of alll types that are not proper nouns (like names). Therefore, concrete nouns will generally be common nouns as well. The distinction with concrete nouns is with abstract nouns (like 'love') which have no physical existence, which again are usually common nouns as well.