An abstract noun is a type of noun that refers to concepts, ideas, emotions, qualities, or states that cannot be perceived by the senses. Unlike concrete nouns, which represent physical and tangible objects, abstract nouns are intangible and often represent things that exist in the mind or have no physical form. Examples of abstract nouns include words like “love,” “happiness,” “knowledge,” “freedom,” “anger,” and “beauty.” These nouns play a crucial role in language by allowing us to discuss and describe intangible concepts and emotions.