Here's why:
* Abstract nouns represent ideas, concepts, qualities, or states of being. They cannot be physically touched or seen.
* Concrete nouns refer to physical things that can be touched, seen, or otherwise experienced with our senses.
Examples:
* Abstract: Communication, love, freedom, happiness, justice
* Concrete: Table, book, dog, flower, car
Communication and vulcanization represent processes or concepts, not tangible things. You can't hold "communication" in your hand, and "vulcanization" isn't something you can see or touch.