Theory:

It can be difficult to recognize when a noun is abstract because there are so many words that can function in different ways. An abstract noun is a naming word that names a cognitive or abstract concept. Things referred to by abstract nouns are those things we can practically talk about, so they do exist in some sense, but we cannot experience them directly with our senses.
Example:
1. Raksha has great taste in dressing. (abstract noun)
    (Here "taste" means understanding)
    Raksha could taste lemon in the pasta. (verb)
    (Whereas here "taste" means aroma)
 
2. Working for Reliance was a childhood dream come true. (abstract noun)
    ( Here "dream" has a similar meaning to hope)
    When I was a little kid, I used to have a  recurring dream about Popeye. (concrete noun)
    ( Whereas here "dream" is similar to fancy)
Important!
Classifying a noun as abstract or concrete may depend on the context or even the classifier's definition of perceivable.
Example:
Numbers
Feelings
States
Ideas
Moments
1.
Hate
Bravery
Dedication
Education
2.
Anger
Honesty
Liberty
Progress
3.
Peace
Integrity
Faith
Relaxation
4.
Sympathy
Courage
Justice
Trouble
5.
Love
Skill
Dream
Friendship
Important!
Click here more examples of abstract noun.