What are concrete and abstract nouns?

Instances of Concrete Noun are tree, phone, football, waterfall, etc. These are those nouns which can be seen, touched and felt. They are tangible and thus have a unique identity. It is something which is recognizable through the senses.

Abstract Nouns are nouns which describe a quality, idea, thought, expression or any other state of being. They are immaterial, the things which cannot be seen or touched but only felt. Instances are childhood, justice, anger, etc.