Final answer:
The three qualities that are the reason for the functional or closed category are Universality, Diversity, and Stability.
Step-by-step explanation:
The three qualities that are the reason for the functional or closed category are Universality, Diversity, and Stability. Universality means that the category is present in all languages, while diversity refers to the wide range of elements that fall under the category. Stability implies that the category remains relatively constant over time.