Theory:

An abstract noun is an intangible concept includes liberty, anger, freedom, love, generosity, charity, and democracy. Notice that these nouns express ideas, concepts, or qualities that cannot be seen or experienced. We cannot see, hear, touch, taste, or smell these concepts.
Usage: Like other nouns, abstract nouns can be used as the subject or object in a sentence.
Example:
1. Anger is not good for health.
(Anger - subject)
 
2. Mother's love is unconditional.
(Mother's love - subject)
 
3. India got freedom in 1947.
(freedom - object)
Capitalization: Abstract nouns are not capitalized when they occur within a sentence.
Example:
1. I want to see justice served.
2. Don’t underestimate your strength.
3. We have to get at the truth of the matter.
Abstract nouns can be countable or uncountable (mass). They can also be singular or possessive. Abstract nouns follow the same grammar rules as other nouns.
Example:
Emotions/Feelings: Love, Hate, Anger, Peace, Pride, Sympathy.
 
States/Attributes: Bravery, Loyalty, Honesty, Integrity, Compassion, Charity, Success, Courage, Deceit.
 
Ideas/Concepts/Ideals: Belief, Dream, Justice, Truth, Faith, Liberty, Knowledge, Thought, Information, Culture, Trust, Dedication.
 
Movements/Events: Progress, Education, Hospitality, Leisure, Trouble, Friendship, Relaxation.
Forming abstract nouns using suffixes: Abstract forms of nouns are very common and important part of communication. In many cases, these nouns are derived by adding a suffix to the root word.
Example:
1. Child is a concrete noun, but childhood is an intangible state, so it is abstract.
2. Honest is an adjective, but honesty is an abstract noun.
3. Friend is a common noun, but friendship is an abstract noun.
Nouns with the following suffixes are often abstract:
 
-tion
-ism
-ity
-ment
-ness
-age
-ance
-ence
-ship
-ability
-acy