Excellent definition of Abstract noun

Abstract noun:-
A noun for example goodness or freedom, that refers to an idea  or general quality not a physical.
A noun relating to or involving general ideas or qualities rather than specific people, objects, or actions.
Examples in sentence
 has been much happier ever since she moved.
He's feeling sad because his pet died.
People were sad that he was leaving.
The experience left her sadder but wiser.
We owe our freedom to the untold numbers of soldiers who have fought in our nation's wars since its founding.
As special guests of the owners, the youngsters had full freedom of the resort and its private beach.
She showed no fear.
Her fears for her son's safety.
A long rest will do you good.
We should all work together for our own goodness
Money will never make you happy. 
References:
Oxford dictionary 7th
Merriam Webster dictionary
Macmillan dictionary