A bittersweet longing for things, persons, or situations of the past. The condition of being homesick; homesickness. The term was originally coined by Johannes Hofer, a medical student in 1678 to refer to "the pain a sick person feels because he wishes to return to his native land, and fears never to see it again".
This neologism was so successful that people forgot its origin. Moreover, its original meaning--referring to a serious medical disorder--has been lost as the word nostalgia entered everyday language.
Nostalgia is more commonly referred to not as a medical condition or a field of study, but as a feeling that any normal person can have. Nostalgia can often be associated with a fond childhood memory, a certain game or activity, often with a certain person, or a treasured personal object.
As Baby Boomers we all have those special moments and treasures that bring us comfort and joy.