The word sthenic originates from the Greek word sthenos, meaning "strength." It refers to something marked by vigor, vitality, or robust physical or mental health. Commonly used in medical or physiological contexts, sthenic describes a state of heightened energy or activity. For example, a "sthenic fever" might denote a fever accompanied by increased vitality and bodily strength, in contrast to more debilitating conditions. It conveys an image of liveliness and resilience, emphasizing the power of energy and force.

In a broader sense, sthenic can also describe a personality or mood characterized by dynamic energy or assertiveness. This term finds relevance not only in medicine but also in everyday descriptions of people or phenomena that exude vigor and robustness, celebrating life's inherent dynamism.