1. a wistful desire to return in thought or in fact to a former time in one's life, to one's home or homeland, or to one's family and friends; a sentimental yearning for the happiness of a former place or time.
2. something that elicits or displays nostalgia.
Nostalgia is a cat that sleeps,
Purring softly under your skin
Only to be startled
By an incomprehensible dream.
L'île de la Cité And la Place Dauphine
6 hours ago