Abstract nouns are mental words which cannot be physically experienced as can a cup, coat, house, bridge, or road, etc., but which only appeals to the mind. Abstract nouns name the categories of the things of our world, for examples intelligence, beauty, progression, indignation, aggression, hostility, arrangement, sacrifice, determination, greed, jealousy, optimism, failure, attentiveness, negligence, salt, pepper, coffee, rice, fish, dairy, confectionery, clothing, luggage, furniture, kitchenware, cutlery, equipment, machinery, stationery, entertainment, architecture. So, although an abstract noun cannot be seen, heard, smelled, touched, or tasted, it can refer to concrete nouns which represent the idea, or an adjective can be added to the concept to specify an aspect of focus of the abstract noun
The abstract noun are states, qualities, feelings, events and concepts etc. E.g. Happiness, music, idea, freedom etc.