Adynamy is a term used to describe a sense of lethargy or lack of energy. While this word has a specific medical meaning, there are many synonyms that can be used to describe a similar feeling. These include words like fatigue, exhaustion, weariness, and listlessness. Each of these words describes a feeling of tiredness or weakness, but they may be used in different contexts. For example, fatigue may be more commonly used to describe physical exhaustion after exercise, while listlessness may be used to describe a lack of motivation or enthusiasm. Regardless of which synonym is used, they all convey a sense of physical or mental sluggishness.