Taiwan is also known as Formosa. Home to the Republic of China (ROC), not to be confused with the Peoples Republic of China (PRC).
That would be Taiwan.
formosa
Taiwan (formally Formosa)
Taiwan was formerly known as Formosa
It is formally known as the Republic of China. Taiwan was named Formosa ("beautiful [island]") by Portuguese explorers, so Westerners did know the island as "Formosa" until the 20th century. On mainland China, Taiwan is written 台湾, and spelled Táiwan in pinyin. On Taiwan, the name is written 臺灣, and spelled Taiwan or T'ai-wan in roman letters. The difference in Chinese characters has to do with the fact that on mainland China they now use "simplified characters" that the Taiwanese do not use. When the Dutch were running a colonial trade company based on Taiwan, they also used the spelling Tayoan, which is pronounced the same as "Taiwan."
The Republic of China is better known as Taiwan.
In most cases, you probably want formerly known as, referring to an old name that is no longer used. For example, "Benin, formerly known as Dahomey, is a country in West Africa."In the alternative, formally known as refers to a fancy name that is usually abbreviated in ordinary use. For example, "The UK, formally known as the United Kingdom of Great Britain and Northern Ireland, is a country in Europe."
The Nationalist Chinese retreated to the island of Taiwan.
The Apache Tomcat was formally known as Jakarta Tomcat.
russia was formally known as the soviet union
Coin collecting is formally known as "numismatics" and people who participate in numismatics are known as numismatists.
This group was formally known as the National Socialists, but they are better known as the Nazis.