Which of the following is a synonym for 'languid'?

The term 'languid' describes a state of weakness or fatigue, often characterized by a lack of energy or vitality. Therefore, 'sluggish' serves as an appropriate synonym because it conveys a similar sense of lethargy and low energy. In contexts where someone might feel languid, the experience often involves a weariness that makes them slow-moving or inactive, perfectly aligning with the definition of sluggish.

The other choices, while they may describe various types of activity, do not align with the meaning of 'languid.' For instance, 'vigorous' and 'energetic' represent the opposite quality, implying liveliness and high energy. 'Aggressive' suggests a forceful or hostile nature, which also does not match the connotation of being languid. Thus, sluggish is the only word that accurately captures the essence of a lack of energy or vitality synonymous with languid.