Step 1: Understanding the Concept:
Educational psychology categorizes human learning domains into knowledge (cognitive), attitude (affective), and skill (psychomotor).
Step 2: Detailed Explanation:
Knowledge represents the theoretical understanding of facts, principles, and concepts.
Skill is the practical competency, ability, and proficiency to apply acquired knowledge effectively to perform physical or mental tasks with dexterity and precision.
Step 3: Final Answer:
Hence, the competency of using knowledge is called skill.