sternly

This adverb conveys a sense of rigid authority and lack of leniency. It is typically used to describe communication or facial expressions intended to intimidate, correct, or command obedience. The tone is cold and uncompromising, often associated with figures of power such as parents, judges, or military officers.

Because it describes a specific manner of behavior, it is most frequently paired with verbs of perception or communication, such as look, warn, reprimand, or state. It differs from "seriously" in that it implies a desire to enforce a rule or express disapproval, whereas "seriously" may simply indicate a lack of humor or a grave situation.