verb A word that expresses an action, occurrence, or state of being. In this case, 'be' is a verb indicating a state of being.
adverb A word that modifies or describes a verb, adjective, or other adverb. 'Still' is an adverb modifying the verb 'be', indicating that the action should be done quietly or without movement.
noun a state of being quiet and peaceful
adjective describing something that is calm and without movement