In the Diaspora, an additional day is celebrated, the second day being separately referred to as Simchat Torah. Shulchan Arukh, Orach Chayim 669 In Israel and Reform Judaism, the holidays of Shemini Atzeret and Simchat Torah are combined into a single day and the names are used interchangeably.
The minhag of the chassidim is to make Kiddush in the Sukkah, but to eat the main meal inside. ; however, one of Sukkot's liturgical aliases , "Time of Our Happiness," continues to be used to describe Shemini Atzeret in prayers.
Source: Wikipedia > Shemini Atzeret
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