Ghost (noun)

1. The spirit of a dead person, especially one believed to appear to the living as a pale, shadowy, or fleeting vision.
2. A false image or spurious signal on a television screen.
3. A faint trace or suggestion of something.

Origin:

Middle english gost, going back to old english gāst 'breath, soul, ghost', going back to germanic *gaistaz, from indo-european *ǵh₂éstus.

Examples:

1. People believe that the ghost of the former owner still haunts the castle.
2. He saw a ghost on the television screen when there was no one there.
3. The smell of freshly baked cookies still lingered in the air, a ghost of the baking session that had just taken place.
4. I can see the ghost of your smile, but I cannot feel its warmth.
5. She felt the ghost of his touch, but she knew it was just her imagination.