NOSTALGIA. The elusive word "nostalgia" is formed from two Greek roots: nostos ("return home") and algia ("pain"). The Oxford English Dictionary defines nostalgia as "a form of melancholia caused by prolonged absence from one's home or country; severe homesickness." In her remarkable book The Future of Nostalgia, Harvard professor Svetlana Boym says that the word was coined in 1688 by the Swiss doctor Johannes Hofer to identify the homesickness of Swiss soldiers who reacted physically to the hearing of certain folk melodies and the eating of rustic soups while on missions away from home. She centers her study on the effects of leaving one culture and residing in another, and of exploring cities rich in archaeological layers of memory. She also distinguishes nostalgia as either being restorative, as in recovering a lost home, or reflective, as in shaping a certain way of thinking about a particular time...