* Abstract nouns refer to concepts, ideas, qualities, or feelings. They are intangible. Examples include: *love, happiness, justice, time*.
* Concrete nouns refer to things you can experience with your senses (sight, touch, smell, taste, sound). Examples include: *book, tree, music, smell*.
Marvel can be both abstract and concrete, depending on how it's used:
* Abstract: When "marvel" refers to the feeling of wonder and amazement, it is abstract. For example: "She felt a sense of marvel at the beauty of the sunset."
* Concrete: When "marvel" refers to something that causes wonder, it's concrete. For example: "The Great Wall of China is a marvel of engineering."
In short:
* Marvel is an abstract noun when it refers to the feeling of amazement.
* Marvel is a concrete noun when it refers to the thing that causes amazement.