The words we use to describe our emotions ultimately affect how we feel, says historian Tiffany Watt Smith, and they've often changed (sometimes very dramatically) in response to new cultural expectations and ideas. Take nostalgia, for instance: first defined in 1688 as an illness and considered deadly, today it's seen as a much less serious affliction. In this fascinating TED-talk about the history of emotions, learn more about how the language we use to describe how we feel continues to evolve… and pick up some new words used in different cultures to capture those fleeting feelings in words.