Sluggishness is the state of moving, working, or reacting more slowly than it should. It is the noun for 'sluggish'. You can use it for a body: after a heavy lunch, or when you are sick, or when you have not slept, you feel a heaviness and a slowness — that is sluggishness. You can also use it for machines and systems: a computer that takes three seconds to open a window, an old car that does not speed up when you press the pedal, a river that barely moves. Business writers and news writers use it for money too: 'sluggishness in the housing market' means the market is still moving, just slowly and weakly. Notice that word 'still' — sluggishness is not stopping. A dead engine is not sluggish; a dead market is not sluggish. Sluggishness always means something IS going, but going slowly, heavily, without energy, when we expected better. There is usually a small feeling of complaint in it. When you call something sluggish, you are saying it should be faster than this. That is why nobody says a sleeping cat shows sluggishness — a sleeping cat is doing exactly what it should. The word is a bit formal, longer than everyday talk. In conversation people are more likely to say 'I feel really slow today' or 'my laptop is so slow'. You will meet 'sluggishness' more in writing — a doctor's note, a news report, a review of a phone.

遲鈍、行動遲緩；講身體時是「昏沉、提不起勁」,講機器或網站時中文更常說「跑得慢、反應慢」,講經濟則說「疲軟」