This week's sales milestone earns Adele -- and "21" -- Diamond Certification by the Recording Industry Association of America. Adele is the only British or European female artist in history to earn this certification, the record label said.
More than 25 million copies of "21" have been sold worldwide.
"What an incredible honor," Adele said in a statement, "a huge, huge thank you to my American fans for embracing this record on such a massive level."
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