Silence !
Silence = Noun = Complete absence of sound.
But does it exist ?
Certainly not during daylight hours - life is noisy !
Even at night, in the depth of winter in the middle of the North Yorkshire Moors it is not silent. There are murmurings and rustlings all about. Lying in bed with all the double glazed windows closed - there still are sounds. Distant traffic, the comforting creaking of the sleeping house.
In a vacuum? Maybe - but how would you know ? Put a man in space suit into a vacuum - instant sound. His breathing, his heartbeat, the hum of whatever measuring instruments he took in there with him.
So - does silence actually exist ?