An abstract noun is the name of a quality, action or state which we can only think of. Examples are: kindness, goodness, honesty, bravery, ignorance, stupidity, wisdom, laughter etc.
Note that the names of arts and sciences are also considered abstract nouns.
Abstract nouns are formed from adjectives, verbs or common nouns. For example, the abstract noun kindness is formed from the adjective kind whereas the abstract noun obedience is formed from the verb obey.
Countable and Uncountable Nouns
Nouns are also classified as countable and uncountable. Countable nouns are the names of objects that we can count. Examples are: book, pen, apple, doctor, sister, boy etc. Uncountable nouns are the names of things which we cannot count. Examples are: rice, gold, wheat, honesty, beauty, oil etc.
Note that countable nouns have plural forms and can be used with the indefinite article a/an. Uncountable nouns do not have plural forms and cannot be used with the indefinite articles.