Here's why:
* Gracious is an adjective that describes someone or something as polite, kind, and courteous.
* Grace is the abstract concept of elegance, beauty, and kindness.
For example, you might say:
* "She showed grace in her acceptance speech." (Here, "grace" is the abstract noun representing the quality of her speech.)
* "He was gracious to his guests." (Here, "gracious" is the adjective describing his behavior.)