Here's why:
* Abstract nouns represent concepts, ideas, qualities, or states of being. Examples: happiness, freedom, love, justice.
* Concrete nouns represent things that can be perceived with the senses (sight, touch, smell, taste, hearing).
Carnival is a concrete noun because it refers to a specific event or celebration that you can experience with your senses. You can see the colorful decorations, hear the music, smell the food, and feel the energy of a carnival.