The term "21st" typically refers to the 21st century, which began on January 1, 2001, and will end on December 31, 2100. This century is characterized by rapid advancements in technology, globalization, and significant social changes. Major events include the rise of the internet, mobile communication, and increased awareness of climate change. In addition to the century, "21st" can also refer to the 21st day of a month or the ordinal number used to denote position in a sequence. For example, 21st Amendment to the United States Constitution repealed Prohibition, and 21st birthday is often celebrated as a significant milestone in many cultures.